fix(scripts): sequence-token race + comment/import cleanup (Codex ffec234 follow-up)

Codex review of ffec234 flagged:

1. **MEDIUM — loadScriptCount in-flight race on workspace switch.**
   Previous implementation used `if (get().scriptCountLoading) return`
   to dedupe. That meant switching workspaces WHILE a fetch was in
   flight dropped the new fetch entirely; the stale response from the
   previous workspace then overwrote state, leaving the dashboard
   showing workspace A's total while the user is on workspace B.
   Fix: drop the dedupe-via-flag, use a module-level
   `_scriptCountSeq` counter. Every call increments, captures the
   seq at start, and the response/finally block only mutates state
   when `_scriptCountSeq === seq` — stale responses are silently
   dropped. Rapid workspace switches each get their own fetch; only
   the latest response wins.

2. **LOW — scriptCount scope comment was misleading.**
   "范围与 list_scripts(parent_path=\"\") 对齐" is wrong: the
   count includes all descendant depths, not just root-level.
   Behaviour is correct for the dashboard's "全部脚本" intent but
   the comment would mislead the next maintainer. Rewritten to
   explicitly call out that the count is the UNION across all
   parent_path depths, with the rationale for each design choice.

3. **LOW — local `from backend.scripts import _escape_like_pattern`
   inside `resources.py` keyword-search block.**
   The "avoid cycle" justification was false: scripts.py and
   resources.py don't import each other at module level. Moved to
   the top-of-file import block.

Skipped:
- get_workspace_tree `like_prefix` not run through the escape helper
  (user_id is a 26-char Crockford ULID so no `_`/`%` can appear, but
  the invariant is not documented at the call site). Pre-existing
  pattern; out of scope for this round.

Verified: pytest 65 passed; pnpm typecheck clean.

frontend/app/features/platform/state/scriptWorkspaceStore.ts

@@ -40,6 +40,7 @@ let _api: WorkspaceBoundApi | null = null;
 let _previewController: AbortController | null = null;
 let _previewRequest = 0;
 let _pythonEditorOpeningIds = new Set<string>();
+let _scriptCountSeq = 0;
 
 export const bindScriptWorkspaceApi = (api: WorkspaceBoundApi | null) => {
   _api = api;
@@ -397,17 +398,25 @@ export const useScriptWorkspaceStore = create<State>((set, get) => {
 
     loadScriptCount: async () => {
       const api = requireApi();
-      if (get().scriptCountLoading) return;
+      // Always fire — don't dedupe via the loading flag. Rapid workspace
+      // switches would otherwise drop the new fetch and leave the
+      // dashboard showing the previous workspace's count. The sequence
+      // counter below discards stale responses instead.
+      const seq = ++_scriptCountSeq;
       set({ scriptCountLoading: true, scriptCount: null });
       try {
         const total = await api.countScripts();
+        if (_scriptCountSeq !== seq) return; // a newer fetch superseded us
         set({ scriptCount: total });
       } catch {
+        if (_scriptCountSeq !== seq) return;
         // Leave previous value in place; the dashboard already tolerates
         // a stale count by rendering `scriptCount ?? 0`. Don't toast —
         // the dashboard's other metrics are best-effort.
       } finally {
-        set({ scriptCountLoading: false });
+        if (_scriptCountSeq === seq) {
+          set({ scriptCountLoading: false });
+        }
       }
     },