feat: add session review handoff flow

Introduce a desktop/web-only /handoff-review flow that generates a handoff from the active implementation session, creates or reuses a separate review session in the same directory, and links the pair through hidden OpenChamber session metadata.

Add review flow orchestration, metadata helpers, magic prompts, localized command/action labels, session metadata create/update support, and assistant message transfer actions for sending reviewer feedback back to the implementer or implementation responses back to the reviewer.

Review sessions are ordinary sessions, not child sessions. The flow avoids exposing session IDs or routing metadata to agents, hides review controls on mobile and VS Code, hides unrelated assistant actions inside review sessions, cleans up stale metadata where possible, and uses the optimistic send path so cross-session sends scroll like normal composer messages.

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

@@ -1611,6 +1611,7 @@ export const dict: Record<I18nKey, string> = {
   'chat.commandAutocomplete.command.compactDescription': '使用 AI 壓縮會話歷史以減少上下文大小',
   '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': '審查工作區 diff 的意圖、正確性與充分性，並依嚴重程度分級。',
+  'chat.commandAutocomplete.command.handoffReviewDescription': '根據生成的交接內容建立或重用獨立的審查會話。',
   '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。',
@@ -1737,6 +1738,8 @@ export const dict: Record<I18nKey, string> = {
   'snippets.source.project': '項目',
   'chat.chatInput.toast.compactFailed': '壓縮會話失敗',
   'chat.chatInput.toast.summaryFailed': '生成總結失敗',
+  'chat.messageBody.actions.sendReviewFeedback': '將審查回饋傳送給實作變更的代理',
+  'chat.messageBody.actions.sendImplementationResponse': '將實作回應傳送給審查代理',
   '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',