feat: add /catch-up and /debug guided commands to draft welcome

Replace the 'What changed recently' draft chip with /catch-up, a command
whose hidden prompt branches on git state: reconstruct intent from an
in-progress diff, check an open PR's review state, or summarize recent
commits.

Add /debug as a new draft chip and command: a guided root-cause
investigation that captures the symptom, forms hypotheses, checks them
against the code, and confirms the cause before proposing a fix.

Both follow the /workspace-review pattern — visible + hidden magic
prompts wired into command autocomplete, the submit handler, draft preset
chips, and the Magic Prompts settings page, with i18n across all locales.

packages/ui/src/lib/i18n/messages/zh-TW.ts

@@ -1418,9 +1418,9 @@ export const dict: Record<I18nKey, string> = {
   'chat.emptyState.draftTitleWithProject': 'What are we working on in {project}?',
   'chat.draftPresets.explore.label': 'Explore the codebase',
   'chat.draftPresets.explore.prompt': 'Give me a high-level tour of this codebase — the architecture, the main modules, and how they fit together.',
-  'chat.draftPresets.changes.label': 'What changed recently',
-  'chat.draftPresets.changes.prompt': 'Summarize what changed recently — the latest commits and the current state of this branch.',
+  'chat.draftPresets.catchup.label': 'Catch me up',
   'chat.draftPresets.plan.label': 'Start feature planning',
+  'chat.draftPresets.debug.label': 'Debug an issue',
   'chat.draftPresets.review.label': 'Review my changes',
   'chat.scrollToBottom.aria': '捲動到底部',
   'chat.timeline.relative.justNow': '剛剛',
@@ -1483,6 +1483,8 @@ export const dict: Record<I18nKey, string> = {
   'chat.commandAutocomplete.command.summaryDescription': '非破壞性會話總結。命令後可選填主題提示。',
   'chat.commandAutocomplete.command.workspaceReviewDescription': '僅審查目前工作區中高價值的問題。',
   'chat.commandAutocomplete.command.featurePlanDescription': '為新功能開始一次引導式的來回規劃工作階段。',
+  'chat.commandAutocomplete.command.catchUpDescription': '重新進入上下文：你之前在做什麼、從哪裡繼續。',
+  'chat.commandAutocomplete.command.debugDescription': '在提出修復方案前，引導式地排查 bug 的根本原因。',
   'chat.commandAutocomplete.badge.skill': 'Skills',
   'chat.commandAutocomplete.badge.command': '命令',
   'chat.commandAutocomplete.badge.system': '系統',
@@ -1599,6 +1601,8 @@ export const dict: Record<I18nKey, string> = {
   'chat.chatInput.toast.summaryFailed': '生成總結失敗',
   'chat.chatInput.toast.reviewFailed': '審查變更失敗',
   'chat.chatInput.toast.planFeatureFailed': '無法開始功能規劃',
+  'chat.chatInput.toast.catchUpFailed': '無法取得上下文',
+  'chat.chatInput.toast.debugFailed': '無法開始除錯',
   'chat.chatInput.toast.attachmentsTooLarge': '附件過大，無法傳送。請減少圖片數量或大小。',
   'chat.chatInput.toast.sendAttachmentsFailed': '傳送附件失敗。請嘗試更少檔案或更小圖片。',
   'chat.chatInput.toast.messageSendFailed': '訊息傳送失敗，附件已恢復。',