refactor: extract drop indicator rect helper

design/05-editor-mainline/process/5-29-editor-runtime-followup-checklist-v1.md

@@ -250,4 +250,7 @@ UI / 浏览器可见项必须有真实浏览器截图或结构化 smoke 证据
   - 未迁：`hovered_block_from_target` 的壳层函数、`drop_indicator_from_target`、拖拽 listener、block reorder 行为仍留在 `lib.rs`。
 - 2026-05-25：Batch AD 出现未由主控明确派发的 3 个 Reasonix runner（Worker B/C/D），超过当前 2-worker 上限；主控已终止相关 runner / ACP 进程。
   - 涉及 worktree：`/mnt/Data1T/mnote-worktrees/0525-ad-worker-b-5-29-drop-indicator-block-rect`、`/mnt/Data1T/mnote-worktrees/0525-ad-worker-c-3-20-upload-target-readonly`、`/mnt/Data1T/mnote-worktrees/0525-ad-worker-d-regression-smoke`。
-  - 本文件不采纳 Batch AD 的任何 5-29 输出；后续如需继续 `drop_indicator_from_target` / block rect 小切片，必须重新按最多 2 worker 的受控批次派发。
+  - Codex 未按 Reasonix 结果直接采纳；随后独立复核 Worker B 遗留 diff，确认范围只涉及 `drop_indicator_from_target` 内部 block/stage rect 读取封装，并选择性合入。
+  - 修改：`editor_runtime/block_dnd.rs` 新增 `drop_indicator_from_block_rects(block_index, block, stage, client_y)`；`lib.rs::drop_indicator_from_target` 仍负责 hovered block、root/stage DOM 查询和 shell 状态，只委托新 helper 计算 `DropIndicatorState`。
+  - 边界：未迁 `drop_indicator_from_target` 壳层函数、`drop_indicator_from_point`、拖拽 listener、block reorder 行为或 Leptos signal 编排；Worker C/D 输出不采纳。
+  - 已验证：`cargo fmt --manifest-path rust/Cargo.toml --all --check`、`git diff --check`、`cargo check --manifest-path rust/spikes/leptos-tiptap-spike/Cargo.toml`、wasm release build、`wasm-bindgen`、`MNOTE_WEB_SMOKE_BASE_URL=http://127.0.0.1:3001 NODE_PATH=/mnt/Data1T/mnote/node_modules node scripts/task489-block-menu-delete-undo-smoke.js`、`MNOTE_WEB_SMOKE_BASE_URL=http://127.0.0.1:3001 NODE_PATH=/mnt/Data1T/mnote/node_modules node scripts/task488-local-attachment-link-delete-undo-smoke.js`、`MNOTE_WEB_SMOKE_BASE_URL=http://127.0.0.1:3001 NODE_PATH=/mnt/Data1T/mnote/node_modules node scripts/task479-local-folder-markdown-resource-lifecycle-smoke.js`。

rust/spikes/leptos-tiptap-spike/src/editor_runtime/block_dnd.rs

@@ -107,6 +107,23 @@ pub(crate) fn direct_block_index_from_element(
     top_level_block_index(root, &block)
 }
 
+pub(crate) fn drop_indicator_from_block_rects(
+    block_index: usize,
+    block: &Element,
+    stage: &Element,
+    client_y: i32,
+) -> DropIndicatorState {
+    let block_rect = block.get_bounding_client_rect();
+    let stage_rect = stage.get_bounding_client_rect();
+    drop_indicator_from_geometry(
+        block_index,
+        block_rect.top(),
+        block_rect.height(),
+        stage_rect.top(),
+        client_y,
+    )
+}
+
 pub(crate) fn top_level_block_index(root: &Element, block: &Element) -> Option<usize> {
     let children = root.children();
     (0..children.length()).find_map(|index| {

rust/spikes/leptos-tiptap-spike/src/lib.rs

@@ -22,8 +22,8 @@ use web_sys::{
 
 use editor_runtime::attachment_upload::dispatch_editor_upload_request;
 use editor_runtime::block_dnd::{
-    direct_block_from_element, direct_block_index_from_element, drop_indicator_from_geometry,
+    direct_block_from_element, direct_block_index_from_element,
-    element_within_handle_shell, event_target_from_point,
+    drop_indicator_from_block_rects, element_within_handle_shell, event_target_from_point,
     pointer_in_handle_corridor_geometry, top_level_block_index, HandleCorridorGeometry,
 };
 use editor_runtime::block_menu_overlay;
@@ -5218,13 +5218,10 @@ fn drop_indicator_from_target(
     let root = editor_root_element()?;
     let block = root.children().item(hovered.index as u32)?;
     let stage = editor_stage_element()?;
-    let block_rect = block.get_bounding_client_rect();
+    Some(drop_indicator_from_block_rects(
-    let stage_rect = stage.get_bounding_client_rect();
-    Some(drop_indicator_from_geometry(
         hovered.index,
-        block_rect.top(),
+        &block,
-        block_rect.height(),
+        &stage,
-        stage_rect.top(),
         client_y,
     ))
 }