✨ feat(vscode): 「改动」面板加审查勾 + deepseek 增量生成文件改动说明

右栏 diff 头部加一组按钮:
- 审查对勾:与左树同一状态源,勾上则文件路径标题置灰
- ✨ 一键调 deepseek 生成该文件「一句话改动目的」

增量复用会话:首个文件开新 cc 会话并把 sessionId 记到
.spx/pr-file-summaries.json,后续文件 --resume 接上去,省去每次重新
理解 PR 的开销;resume 失败则丢弃旧 id 重开一次。说明也落盘(跨 push
保留),重载后仍显示。

- spawnClaude 增 resumeSessionId(--resume)
- 新增 prFileSummaryStore;handler handleGeneratePrFileSummary
  用 jsdiff 拼 unified diff 喂模型
- 依赖 diff(jsdiff)

vscode/webview-ui/src/lib/messages.ts

@@ -115,8 +115,9 @@ export type ExtensionToWebview
     | { type: 'issue/remove', issueNumber: number }
     | { type: 'profiles/show', data: ProfilesData }
     | { type: 'managed-sessions/show', data: ManagedSessionsData }
-    | { type: 'pr-files/show', issueNumber: number, headSha: string, mergeBase: string, files: PrFile[], confirmed: string[], error?: string }
+    | { type: 'pr-files/show', issueNumber: number, headSha: string, mergeBase: string, files: PrFile[], confirmed: string[], summaries: Record<string, string>, error?: string }
     | { type: 'pr-file-diff/show', issueNumber: number, path: string, oldContent: string, newContent: string, oldLang?: string, newLang?: string, error?: string }
+    | { type: 'pr-file-summary/show', issueNumber: number, path: string, summary?: string, error?: string }
 
 export type WebviewToExtension
   = | { type: 'issues/refresh' }
@@ -189,4 +190,5 @@ export type WebviewToExtension
     | { type: 'managed-sessions/close-tab', sessionId: string }
     | { type: 'pr-files/get', issueNumber: number }
     | { type: 'pr-file-diff/get', issueNumber: number, path: string, previousPath?: string }
+    | { type: 'pr-file-summary/generate', issueNumber: number, path: string, previousPath?: string }
     | { type: 'pr-review/set', issueNumber: number, headSha: string, confirmed: string[] }