refactor(admin): 文章搜索框改用 FormInput 公共组件

- AllPostsList 的手写 <input> 替换为 forms::FormInput +
  INPUT_INLINE_CLASS，与 asset_picker / assets 的搜索栏先例统一
  （修正圆角 rounded-lg→rounded-2xl，补 min-w-0 / transition-colors）。
- AGENTS.md Code Conventions 新增第 17 条：编写 rsx 前必须先查
  src/components/{ui,forms}.rs 的现有组件/样式常量，禁止第二套约定。

AGENTS.md

@@ -154,6 +154,7 @@ make docker-multiarch IMAGE=ghcr.io/owner/yggdrasil:latest   # amd64+arm64, push
     - **`unreachable!()` is permitted ONLY in `#[cfg(not(feature = "server"))]` stubs** of server functions — these branches are compiled out of the real server build and exist solely to satisfy the WASM target's type checker.
     - **Build-tool binaries** (`src/bin/*`) and **`#[cfg(test)]` modules** are exempt — `unwrap`/`expect`/`panic` are idiomatic in tests and one-shot codegen tools.
     - **If clippy's `unwrap_used` / `expect_used` lints are later wired in** (`[lints]` table in `Cargo.toml`), the exemptions above are the intended `allow` set; do not relax them further without a documented invariant.
+17. **Reuse shared UI components — never hand-roll a duplicate.** Before writing any `rsx!` element with an inline Tailwind class string, scan `src/components/` for an existing component or style constant and reuse it. Two modules own this surface: `ui.rs` (display atoms — `Pagination`, `StatusBadge`, `Tooltip`, `Popover`, `FilterTabs`, `LoadingButton`; plus class constants `BTN_PRIMARY`/`BTN_PRIMARY_SM`/`BTN_OUTLINE`/`BTN_DANGER_OUTLINE`/`BTN_SECONDARY`/`BTN_TEXT_*`/`BTN_SOLID_*`/`BTN_CLOSE_ICON`/`BTN_ICON`/`ADMIN_CARD_CLASS`/`ADMIN_TABLE_CLASS`/`ADMIN_ROW_HOVER`/`BADGE_BASE`/`CHECKBOX_CLASS`/`SPINNER_SVG`) and `forms.rs` (form controls — `FormInput`, `FormSelect`, `FormLabel`, `AlertBox`; plus class constants `INPUT_CLASS`/`INPUT_INLINE_CLASS`/`BUTTON_PRIMARY_CLASS`/`FORM_SELECT_COMPACT_CLASS`). Use `FormInput` with the right `class` prop (`INPUT_CLASS` = full-width form field, `INPUT_INLINE_CLASS` = flank a button / fill remaining width) instead of a bespoke `<input class="...">`; use `FormSelect` instead of a native `<select>` (OS-rendered popups can't follow the theme). For composite patterns (search bars, filter toolbars, action rows), grep for an existing instance and mirror its structure — e.g. the `FormInput { r#type: "search", class: INPUT_INLINE_CLASS, ... }` flanked by `BTN_PRIMARY`/`BTN_OUTLINE` search bar already lives in `asset_picker.rs` and `assets.rs`. A second convention beside an existing one is PROHIBITED — if the existing component is missing a feature, extend it rather than spawning a parallel one.
 
 ## MCP Server
 

src/pages/admin/posts.rs

@@ -19,6 +19,7 @@ use crate::api::posts::{
     CreatePostResponse, PostStatsResponse, RebuildResult,
 };
 use crate::components::empty_state::{EmptyState, EmptyStateAction};
+use crate::components::forms::{FormInput, INPUT_INLINE_CLASS};
 use crate::components::skeletons::delayed_skeleton::DelayedSkeleton;
 use crate::components::skeletons::posts_skeleton::PostsSkeleton;
 use crate::components::ui::{
@@ -190,13 +191,13 @@ fn AllPostsList() -> Element {
     rsx! {
         // 搜索条：按标题过滤文章（仅管理后台用，覆盖草稿）。
         div { class: "flex gap-2 mb-4",
-            input {
+            FormInput {
-                class: "flex-1 px-4 py-2 border border-paper-border rounded-lg bg-paper-entry text-paper-primary placeholder:text-paper-tertiary focus:outline-none focus:border-paper-accent focus:ring-1 focus:ring-paper-accent/30",
+                r#type: "search",
-                r#type: "text",
                 placeholder: "搜索文章标题...",
-                value: "{search_input()}",
+                value: search_input(),
-                oninput: move |e| search_input.set(e.value()),
+                class: INPUT_INLINE_CLASS,
-                onkeydown: move |e| {
+                oninput: move |v: String| search_input.set(v),
+                onkeydown: move |e: KeyboardEvent| {
                     if e.key() == Key::Enter {
                         submit_search();
                     }