fix(web): visual QA front-end items U4–U6, U13–U16 and copy list

- U4: form save failures toast the first problem and scroll/focus the first
  invalid field (policy draft, settings cards, resource drawers, subscription
  form) via lib/form-errors.
- U5: FormField keeps 8px between a hint and the next label.
- U6: file manager status bar keeps free space left-aligned, clear of the
  Agent button.
- U13: move/copy dialog stops "target is the source folder / inside the
  source" before requesting a preview (transferTargetProblem + tests).
- U14: account popover uses the solid float material.
- U15/U16: inbox tile hint shortened; TMDB assign dialog uses the shared
  Select and labelled fields (type, TMDB ID, note).
- Copy: "TMDB 已保存" spacing, API Key block no longer repeats the section
  title, whole-day intervals read "每 7 天", "最高级别:提示",
  "延后:已有计划在途", failed records show "未生成目标路径", upstream model
  column "默认模型".

Co-Authored-By: Claude Opus 5.5 <[email protected]>

apps/web/app/lib/form-errors.ts

@@ -0,0 +1,23 @@
+// 表单级错误定位(QA U4):保存失败时滚到第一个出错的字段并聚焦,长表单里不用自己找。
+
+/** 下一帧(错误已渲染)后,在 root 里找第一个 aria-invalid 的控件或 role=alert 的提示,滚到视口中间并聚焦 */
+export function revealFirstError(root?: HTMLElement | null) {
+  if (typeof window === "undefined") return;
+  requestAnimationFrame(() =>
+    requestAnimationFrame(() => {
+      const scope: ParentNode = root ?? document;
+      const el =
+        scope.querySelector<HTMLElement>('[aria-invalid="true"]') ?? scope.querySelector<HTMLElement>('[role="alert"]');
+      if (!el) return;
+      el.scrollIntoView({ block: "center", behavior: "smooth" });
+      if (el.matches("input, textarea, select, button, [tabindex]")) el.focus({ preventScroll: true });
+    }),
+  );
+}
+
+/** toast 用的一句话:"有 3 处需要修改:填写模板名称" */
+export function formErrorSummary(errors: Record<string, string>): string {
+  const msgs = Object.values(errors).filter(Boolean);
+  if (msgs.length === 0) return "表单有错误";
+  return msgs.length === 1 ? `需要修改:${msgs[0]}` : `有 ${msgs.length} 处需要修改:${msgs[0]}`;
+}