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/components/library/subscriptions-policy.tsx

@@ -30,6 +30,7 @@ import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "~
 import { Switch } from "~/components/ui/switch.tsx";
 import { Textarea } from "~/components/ui/textarea.tsx";
 import { errorMessage } from "~/lib/api.ts";
+import { formErrorSummary, revealFirstError } from "~/lib/form-errors.ts";
 import { actorText } from "~/lib/labels.ts";
 import { cn, formatDateTime } from "~/lib/utils.ts";
 import { CANDIDATE_DECISION, MEDIA_KIND, POLICY_STATUS } from "./labels.ts";
@@ -633,7 +634,8 @@ function PolicyEditorSheet({
           open: t.open || Object.keys(r.errors).some((k) => k.startsWith(`${t.key}.`)),
         })),
       }));
-      toast.error("表单有错误");
+      toast.error(formErrorSummary(r.errors));
+      revealFirstError();
       return;
     }
     setErrors({});