feat: “出问题了”三栏说清问题，交作品时写一句反思，外部提示词至少 8 个字

- 对话框加“出问题了”：做了什么 / 想看到什么 / 实际看到了什么拼成一句发给 AI；
  只说“还是不行”这类的提醒一次，可以直接发
- “交这一版”先弹框问最满意的改动和理由（可以不写），存在 submission_reflection，
  批改面板显示为“学生说”，只有老师和作者本人看得到
- 粘贴外部 AI 代码时提示词至少 8 个字，可以把几轮都贴进来

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -30,7 +30,7 @@ The backend was rewritten from Django in 2026-10 to cut memory use (~25 MB vs. 1
   - `src/router.ts` — Vue Router; `meta.auth` needs login, `meta.role` (`staff` = admin+super, `super`) is checked in the guard after `store/session.loadUser()`, `meta.bare` pages render without the top bar
   - `src/theme.ts` — the only place colors are defined: one palette (light + dark values) becomes both `--wp-*` CSS variables and Naive UI `themeOverrides`; use `var(--wp-...)` in styles, never hard-coded colors (iframes stay white: they show students' pages). No `color-mix()` (Chrome 105). `store/theme.ts` holds the mode (auto / light / dark, toggled in the top bar) and sets `data-theme` on `<html>`; `styles/dark-content.css` is generated from the GitHub dark markdown and highlight.js styles (selectors prefixed with `:root[data-theme="dark"]`); CodeMirror uses One Dark highlighting in dark mode
   - `src/icons.ts` — `<Icon icon="lucide:name" />` renders bundled `lucide-vue-next` icons (works offline); register new names in its map. Fonts are bundled too (`@fontsource/jetbrains-mono`)
-  - `components/workbench/Workbench.vue` — shared challenge / creation page: left = brief + AI chat (`PromptPanel`), right = preview / code (`CodeTabs`) + `VersionBar`. Every assistant message with code is a version; hand edits and pasted external-AI code are saved as versions via `POST /prompt/versions` (`source` `edit` / `manual`, stored as a user+assistant pair). Challenges are submitted only when the student clicks “交这一版” (`POST /submission/` with `message_id`), never automatically. Editor code is per task (`composables/useTaskCode.ts`, localStorage `web-code:<user>:<task>`); the tutorial page edits the shared `store/editors.ts` refs but `Workspace.vue` saves them under the same per-task key and `TutorialContent` restores them (example code only the first time)
+  - `components/workbench/Workbench.vue` — shared challenge / creation page: left = brief + AI chat (`PromptPanel`), right = preview / code (`CodeTabs`) + `VersionBar`. Every assistant message with code is a version; hand edits and pasted external-AI code are saved as versions via `POST /prompt/versions` (`source` `edit` / `manual`, stored as a user+assistant pair). Challenges are submitted only when the student clicks “交这一版” (`POST /submission/` with `message_id`), never automatically; `SubmitModal` first asks an optional one-line reflection (最满意的改动和理由), stored in `submission_reflection` (`ON DELETE CASCADE`, returned by `GET /submission/:id` only to staff and the author, shown as “学生说” in `ReviewPanel`). In `PromptPanel`, “出问题了” is a three-field form (做了什么 / 想看到什么 / 实际看到了什么) joined into one prompt; a short vague complaint (“还是不行”) gets a one-time hint offering it. Pasted external-AI prompts need at least 8 characters Editor code is per task (`composables/useTaskCode.ts`, localStorage `web-code:<user>:<task>`); the tutorial page edits the shared `store/editors.ts` refs but `Workspace.vue` saves them under the same per-task key and `TutorialContent` restores them (example code only the first time)
   - `pages/ChallengeHome.vue` — challenge list page; `pages/TaskEditor.vue` (prop `kind`) is the single tutorial / challenge authoring page
   - `pages/Review.vue` (“批改”, default teaching page) + `components/review/ReviewPanel.vue` (also opened from the gradebook) — opens as a large preview (wall hidden, Esc returns; “小面板” switches to a side panel, remembered); keys: J/K previous/next student (by key position), 1–5 rate, P present; “全部班级” groups the wall by class; `components/review/PeersDrawer.vue` is the students' “同学作品” (本班 / 全部班级)
   - `components/layout/AppShell.vue` — top bar for every page; `pages/Dashboard.vue` is the teaching sidebar (“教学”) under `/dashboard`