fix(photo-editor): 修复裁剪 tab 流程与裁剪框拖动

两个问题：
1. 切到裁剪 tab 后还要再点裁剪 icon 才进入裁剪——改为切 tab 即自动进入，
   底部按钮由"开关裁剪"改为"✓ 确认裁剪"，点击烘焙裁剪并保留在 tab。
2. 裁剪框无法移动——重写 CropOverlay 拖动逻辑：
   - 加 BODY 整体平移（拖框内区域平移整框）
   - onDrag 每帧从 state 读实时裁剪值叠加增量，修复闭包快照导致的抖动
   - dragHandle 内聚到组件内部，消除跨重组延迟
   - 抽出 hitHandle/moveCrop，四角与整体均带边界约束防交叉越界

ViewModel 新增 enterCrop/exitCrop/applyCrop，删除 toggleCrop。

core/src/main/kotlin/plus/rua/project/PhotoEditorViewModel.kt

@@ -80,15 +80,44 @@ class PhotoEditorViewModel(
         update { it.copy(rotationDegrees = it.rotationDegrees + delta) }
     }
 
-    /** 开启/关闭裁剪。开启时使用默认居中 4:3 裁剪框。 */
+    /** 进入裁剪模式：启用裁剪框并重置为默认居中区域。 */
-    fun toggleCrop() {
+    fun enterCrop() {
         update {
-            if (it.cropEnabled) {
-                it.copy(cropLeft = null, cropRight = null, cropTop = 0f, cropBottom = 1f)
-            } else {
             it.copy(cropLeft = 0.1f, cropTop = 0.1f, cropRight = 0.9f, cropBottom = 0.9f)
         }
     }
+
+    /** 退出裁剪模式：清空裁剪框（不应用裁剪）。 */
+    fun exitCrop() {
+        update {
+            it.copy(cropLeft = null, cropRight = null, cropTop = 0f, cropBottom = 1f)
+        }
+    }
+
+    /**
+     * 确认裁剪：将当前裁剪框烘焙到源图，用裁剪结果替换 [PhotoEditorState.sourceBitmap]，
+     * 重置旋转与裁剪框，清空手写笔触（坐标系已变化）。
+     */
+    fun applyCrop() {
+        update {
+            if (!it.cropEnabled) return@update it
+            val cropped = PhotoProcessor.crop(
+                bitmap = it.rotatedBitmap,
+                left = it.cropLeft!!,
+                top = it.cropTop,
+                right = it.cropRight!!,
+                bottom = it.cropBottom
+            )
+            it.copy(
+                sourceBitmap = cropped,
+                rotationDegrees = 0,
+                cropLeft = null,
+                cropTop = 0f,
+                cropRight = null,
+                cropBottom = 1f,
+                strokes = emptyList()
+            )
+        }
     }
 
     /** 更新裁剪框比例。 */

core/src/main/kotlin/plus/rua/project/ui/PhotoEditorScreen.kt

@@ -20,7 +20,6 @@ import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Brush
 import androidx.compose.material.icons.filled.ChevronLeft
 import androidx.compose.material.icons.filled.Crop
-import androidx.compose.material.icons.filled.CropFree
 import androidx.compose.material.icons.filled.Done
 import androidx.compose.material.icons.filled.RotateLeft
 import androidx.compose.material.icons.filled.RotateRight
@@ -45,6 +44,7 @@ import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
+import kotlin.math.absoluteValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.geometry.Size
@@ -95,6 +95,14 @@ fun PhotoEditorScreen(
     var activeTab by remember { mutableStateOf(EditTab.ROTATE) }
     val savedPath = state.savedPath
 
+    // 切到裁剪 tab 自动进入裁剪模式；切走则退出（不应用裁剪）
+    LaunchedEffect(activeTab, state.editorState) {
+        when (activeTab) {
+            EditTab.CROP -> viewModel.enterCrop()
+            else -> viewModel.exitCrop()
+        }
+    }
+
     if (savedPath != null) {
         LaunchedEffect(savedPath) { onSaved(savedPath) }
     }
@@ -157,7 +165,7 @@ fun PhotoEditorScreen(
                         activeTab = activeTab,
                         onTabChange = { activeTab = it },
                         onRotate = viewModel::rotate,
-                        onCropToggle = viewModel::toggleCrop,
+                        onApplyCrop = viewModel::applyCrop,
                         onCropChange = viewModel::updateCrop,
                         onAddPoint = viewModel::addStrokePoint,
                         onEndStroke = viewModel::endStroke,
@@ -181,7 +189,7 @@ private fun EditorBody(
     activeTab: EditTab,
     onTabChange: (EditTab) -> Unit,
     onRotate: (Int) -> Unit,
-    onCropToggle: () -> Unit,
+    onApplyCrop: () -> Unit,
     onCropChange: (Float, Float, Float, Float) -> Unit,
     onAddPoint: (Offset) -> Unit,
     onEndStroke: () -> Unit,
@@ -245,7 +253,7 @@ private fun EditorBody(
             mode = activeTab,
             state = state,
             onRotate = onRotate,
-            onCropToggle = onCropToggle,
+            onApplyCrop = onApplyCrop,
             onUndoStroke = onUndoStroke,
             onStrokeColorChange = onStrokeColorChange,
             modifier = Modifier
@@ -265,8 +273,6 @@ private fun EditableImage(
     onDisplaySizeChange: (Float, Float) -> Unit
 ) {
     val rotatedBmp = remember(state.rotationDegrees, state.sourceBitmap) { state.rotatedBitmap }
-    // 裁剪框拖动手柄（CROP 模式下使用）
-    var dragHandle by remember { mutableStateOf<CropHandle?>(null) }
 
     Box(
         modifier = Modifier
@@ -299,8 +305,6 @@ private fun EditableImage(
         if (mode == EditTab.CROP && state.cropEnabled) {
             CropOverlay(
                 state = state,
-                dragHandle = dragHandle,
-                onHandleChange = { dragHandle = it },
                 onCropChange = onCropChange,
                 modifier = Modifier.fillMaxSize()
             )
@@ -324,7 +328,7 @@ private fun EditableImage(
     }
 }
 
-private enum class CropHandle { TOP_LEFT, TOP_RIGHT, BOTTOM_LEFT, BOTTOM_RIGHT, NONE }
+private enum class CropHandle { TOP_LEFT, TOP_RIGHT, BOTTOM_LEFT, BOTTOM_RIGHT, BODY, NONE }
 
 /** 裁剪框四元组，支持解构以简化 onDrag 回传。 */
 private data class CropRect(
@@ -334,16 +338,110 @@ private data class CropRect(
     val bottom: Float
 )
 
+/**
+ * 判断触摸点落在裁剪框的哪个区域，用于决定拖动行为。
+ *
+ * - 落在四角阈值范围内 → 对应角手柄（缩放裁剪框）
+ * - 落在框内 → 整体平移
+ * - 落在框外 → [CropHandle.NONE]，不响应拖动
+ *
+ * @param ox 触摸点 x 比例坐标 [0,1]
+ * @param oy 触摸点 y 比例坐标 [0,1]
+ * @param l/t/r/b 当前裁剪框四边比例
+ */
+private fun hitHandle(
+    ox: Float,
+    oy: Float,
+    l: Float,
+    t: Float,
+    r: Float,
+    b: Float
+): CropHandle {
+    val corner = 0.1f
+    val atTopLeft = (ox - l).absoluteValue < corner && (oy - t).absoluteValue < corner
+    val atTopRight = (ox - r).absoluteValue < corner && (oy - t).absoluteValue < corner
+    val atBottomLeft = (ox - l).absoluteValue < corner && (oy - b).absoluteValue < corner
+    val atBottomRight = (ox - r).absoluteValue < corner && (oy - b).absoluteValue < corner
+    return when {
+        atTopLeft -> CropHandle.TOP_LEFT
+        atTopRight -> CropHandle.TOP_RIGHT
+        atBottomLeft -> CropHandle.BOTTOM_LEFT
+        atBottomRight -> CropHandle.BOTTOM_RIGHT
+        ox in l..r && oy in t..b -> CropHandle.BODY
+        else -> CropHandle.NONE
+    }
+}
+
+/**
+ * 将单次拖动增量应用到当前裁剪框，返回受边界约束的新四元组。
+ *
+ * - 角手柄：只移动对应角，并用 [minSize] 约束避免左右/上下交叉
+ * - [CropHandle.BODY]：整体平移，受 [0,1] 边界约束
+ *
+ * @param dx x 方向增量比例（已归一化）
+ * @param dy y 方向增量比例（已归一化）
+ * @param l/t/r/b 当前裁剪框四边比例
+ * @param handle 本次拖动的手柄
+ * @param minSize 裁剪框最小宽/高比例，防止四角交叉
+ */
+private fun moveCrop(
+    dx: Float,
+    dy: Float,
+    l: Float,
+    t: Float,
+    r: Float,
+    b: Float,
+    handle: CropHandle,
+    minSize: Float = 0.1f
+): CropRect {
+    val left = l.coerceIn(0f, 1f)
+    val top = t.coerceIn(0f, 1f)
+    val right = r.coerceIn(0f, 1f)
+    val bottom = b.coerceIn(0f, 1f)
+    return when (handle) {
+        CropHandle.TOP_LEFT -> {
+            val nl = (left + dx).coerceIn(0f, right - minSize)
+            val nt = (top + dy).coerceIn(0f, bottom - minSize)
+            CropRect(nl, nt, right, bottom)
+        }
+        CropHandle.TOP_RIGHT -> {
+            val nr = (right + dx).coerceIn(left + minSize, 1f)
+            val nt = (top + dy).coerceIn(0f, bottom - minSize)
+            CropRect(left, nt, nr, bottom)
+        }
+        CropHandle.BOTTOM_LEFT -> {
+            val nl = (left + dx).coerceIn(0f, right - minSize)
+            val nb = (bottom + dy).coerceIn(top + minSize, 1f)
+            CropRect(nl, top, right, nb)
+        }
+        CropHandle.BOTTOM_RIGHT -> {
+            val nr = (right + dx).coerceIn(left + minSize, 1f)
+            val nb = (bottom + dy).coerceIn(top + minSize, 1f)
+            CropRect(left, top, nr, nb)
+        }
+        CropHandle.BODY -> {
+            val w = right - left
+            val h = bottom - top
+            val nl = (left + dx).coerceIn(0f, 1f - w)
+            val nt = (top + dy).coerceIn(0f, 1f - h)
+            CropRect(nl, nt, nl + w, nt + h)
+        }
+        CropHandle.NONE -> CropRect(left, top, right, bottom)
+    }
+}
+
 @Composable
 private fun CropOverlay(
     state: PhotoEditorState,
-    dragHandle: CropHandle?,
-    onHandleChange: (CropHandle?) -> Unit,
     onCropChange: (Float, Float, Float, Float) -> Unit,
     modifier: Modifier = Modifier
 ) {
+    // 拖动手柄内聚在此组件，避免跨重组延迟
+    var dragHandle by remember { mutableStateOf(CropHandle.NONE) }
     val left = state.cropLeft ?: 0.1f
+    val top = state.cropTop
     val right = state.cropRight ?: 0.9f
+    val bottom = state.cropBottom
     Canvas(
         modifier = modifier.pointerInput(Unit) {
             detectDragGestures(
@@ -351,45 +449,42 @@ private fun CropOverlay(
                     val size = this.size
                     val ox = offset.x / size.width
                     val oy = offset.y / size.height
-                    onHandleChange(
+                    dragHandle = hitHandle(
-                        when {
+                        ox, oy,
-                            ox < 0.2f && oy < 0.2f -> CropHandle.TOP_LEFT
+                        state.cropLeft ?: 0.1f,
-                            ox > 0.8f && oy < 0.2f -> CropHandle.TOP_RIGHT
+                        state.cropTop,
-                            ox < 0.2f && oy > 0.8f -> CropHandle.BOTTOM_LEFT
+                        state.cropRight ?: 0.9f,
-                            ox > 0.8f && oy > 0.8f -> CropHandle.BOTTOM_RIGHT
+                        state.cropBottom
-                            else -> CropHandle.NONE
-                        }
                     )
                 },
                 onDrag = { change, drag ->
+                    if (dragHandle == CropHandle.NONE) return@detectDragGestures
                     change.consume()
                     val size = this.size
                     val dx = drag.x / size.width
                     val dy = drag.y / size.height
-                    val (nL, nT, nR, nB) = when (dragHandle) {
+                    // 每帧从 state 读最新值，叠加增量
-                        CropHandle.TOP_LEFT ->
+                    val cur = moveCrop(
-                            CropRect(left + dx, state.cropTop + dy, right, state.cropBottom)
+                        dx, dy,
-                        CropHandle.TOP_RIGHT ->
+                        state.cropLeft ?: 0.1f,
-                            CropRect(left, state.cropTop + dy, right + dx, state.cropBottom)
+                        state.cropTop,
-                        CropHandle.BOTTOM_LEFT ->
+                        state.cropRight ?: 0.9f,
-                            CropRect(left + dx, state.cropTop, right, state.cropBottom + dy)
+                        state.cropBottom,
-                        CropHandle.BOTTOM_RIGHT ->
+                        dragHandle
-                            CropRect(left, state.cropTop, right + dx, state.cropBottom + dy)
+                    )
-                        else -> return@detectDragGestures
+                    onCropChange(cur.left, cur.top, cur.right, cur.bottom)
-                    }
-                    onCropChange(nL, nT, nR, nB)
                 },
-                onDragEnd = { onHandleChange(null) },
+                onDragEnd = { dragHandle = CropHandle.NONE },
-                onDragCancel = { onHandleChange(null) }
+                onDragCancel = { dragHandle = CropHandle.NONE }
             )
         }
     ) {
         val w = size.width
         val h = size.height
         val l = left * w
-        val t = state.cropTop * h
+        val t = top * h
         val r = right * w
-        val b = state.cropBottom * h
+        val b = bottom * h
         // 四周遮罩
         drawRect(Color.Black.copy(alpha = 0.5f), topLeft = Offset(0f, 0f), size = Size(l, h))
         drawRect(Color.Black.copy(alpha = 0.5f), topLeft = Offset(r, 0f), size = Size(w - r, h))
@@ -410,7 +505,7 @@ private fun ToolBar(
     mode: EditTab,
     state: PhotoEditorState,
     onRotate: (Int) -> Unit,
-    onCropToggle: () -> Unit,
+    onApplyCrop: () -> Unit,
     onUndoStroke: () -> Unit,
     onStrokeColorChange: (Color) -> Unit,
     modifier: Modifier = Modifier
@@ -430,11 +525,8 @@ private fun ToolBar(
                 }
             }
             EditTab.CROP -> {
-                FilledIconButton(onClick = onCropToggle) {
+                FilledIconButton(onClick = onApplyCrop) {
-                    Icon(
+                    Icon(Icons.Filled.Done, contentDescription = "确认裁剪")
-                        if (state.cropEnabled) Icons.Filled.CropFree else Icons.Filled.Crop,
-                        contentDescription = if (state.cropEnabled) "关闭裁剪" else "开启裁剪"
-                    )
                 }
             }
             EditTab.HANDWRITE -> {