revert(photo-editor): 恢复点击裁剪 icon 进入裁剪的交互

撤销"切到裁剪 tab 自动进入裁剪"的改动，保留原来的两步操作：
点击下方裁剪 icon 进入裁剪模式，再次点击 ✓ 确认裁剪。

ViewModel 恢复 toggleCrop，删除无用的 enterCrop/exitCrop；
保留裁剪框拖动的 bug 修复（本地累积值 + rememberUpdatedState）。

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

@@ -80,18 +80,14 @@ class PhotoEditorViewModel(
         update { it.copy(rotationDegrees = it.rotationDegrees + delta) }
     }
 
-    /** 进入裁剪模式：仅在尚未启用时初始化为默认居中区域，已启用则保留当前框。 */
+    /** 开启/关闭裁剪。开启时使用默认居中 4:3 裁剪框。 */
-    fun enterCrop() {
+    fun toggleCrop() {
-        update {
-            if (it.cropEnabled) it
-            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 {
+            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)
+            }
         }
     }
 

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

@@ -97,14 +97,6 @@ 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) }
     }
@@ -167,6 +159,7 @@ fun PhotoEditorScreen(
                         activeTab = activeTab,
                         onTabChange = { activeTab = it },
                         onRotate = viewModel::rotate,
+                        onCropToggle = viewModel::toggleCrop,
                         onApplyCrop = viewModel::applyCrop,
                         onCropChange = viewModel::updateCrop,
                         onAddPoint = viewModel::addStrokePoint,
@@ -191,6 +184,7 @@ private fun EditorBody(
     activeTab: EditTab,
     onTabChange: (EditTab) -> Unit,
     onRotate: (Int) -> Unit,
+    onCropToggle: () -> Unit,
     onApplyCrop: () -> Unit,
     onCropChange: (Float, Float, Float, Float) -> Unit,
     onAddPoint: (Offset) -> Unit,
@@ -255,6 +249,7 @@ private fun EditorBody(
             mode = activeTab,
             state = state,
             onRotate = onRotate,
+            onCropToggle = onCropToggle,
             onApplyCrop = onApplyCrop,
             onUndoStroke = onUndoStroke,
             onStrokeColorChange = onStrokeColorChange,
@@ -522,6 +517,7 @@ private fun ToolBar(
     mode: EditTab,
     state: PhotoEditorState,
     onRotate: (Int) -> Unit,
+    onCropToggle: () -> Unit,
     onApplyCrop: () -> Unit,
     onUndoStroke: () -> Unit,
     onStrokeColorChange: (Color) -> Unit,
@@ -541,10 +537,16 @@ private fun ToolBar(
                     Icon(Icons.Filled.RotateRight, contentDescription = "右转 90°")
                 }
             }
-            EditTab.CROP -> {
+            EditTab.CROP -> if (state.cropEnabled) {
+                // 已进入裁剪模式：✓ 确认裁剪（烘焙到源图）
                 FilledIconButton(onClick = onApplyCrop) {
                     Icon(Icons.Filled.Done, contentDescription = "确认裁剪")
                 }
+            } else {
+                // 未进入：点击进入裁剪模式
+                FilledIconButton(onClick = onCropToggle) {
+                    Icon(Icons.Filled.Crop, contentDescription = "进入裁剪")
+                }
             }
             EditTab.HANDWRITE -> {
                 IconButton(onClick = onUndoStroke, enabled = state.strokes.isNotEmpty()) {