✨ 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/src/sessions/prFileSummaryStore.ts

@@ -0,0 +1,113 @@
+/**
+ * Workspace 级「PR 文件改动说明 + 续会话 id」持久化。
+ *
+ * 落盘到 `<workspace>/.spx/pr-file-summaries.json`，形状 `Record<string, string>`。
+ * 用前缀给两类值分命名空间，避免「文件路径」与「会话 key」相撞：
+ * - `sum:${issueNumber}:${path}` → 该文件一句话改动说明（跨 push 保留，不随 head sha 失效）。
+ * - `ses:${issueNumber}`         → 该工单最近一次 deepseek 生成会话的 sessionId，供下次 `--resume`。
+ *
+ * 文件不存在或解析失败时按空处理。
+ */
+
+import { promises as fsp } from 'node:fs'
+import * as path from 'node:path'
+
+type SummaryMap = Record<string, string>
+
+function summaryFile(workspaceRoot: string): string {
+  return path.join(workspaceRoot, '.spx', 'pr-file-summaries.json')
+}
+
+function summaryKey(issueNumber: number, filePath: string): string {
+  return `sum:${issueNumber}:${filePath}`
+}
+
+function sessionKey(issueNumber: number): string {
+  return `ses:${issueNumber}`
+}
+
+/** 读出整张映射；文件不存在或解析失败返回空对象。 */
+async function readMap(workspaceRoot: string): Promise<SummaryMap> {
+  let raw: string
+  try {
+    raw = await fsp.readFile(summaryFile(workspaceRoot), 'utf8')
+  }
+  catch {
+    return {}
+  }
+  try {
+    const parsed = JSON.parse(raw) as unknown
+    if (!parsed || typeof parsed !== 'object' || Array.isArray(parsed))
+      return {}
+    const out: SummaryMap = {}
+    for (const [k, v] of Object.entries(parsed as Record<string, unknown>)) {
+      if (typeof v === 'string')
+        out[k] = v
+    }
+    return out
+  }
+  catch {
+    return {}
+  }
+}
+
+async function writeMap(workspaceRoot: string, map: SummaryMap): Promise<void> {
+  const dir = path.join(workspaceRoot, '.spx')
+  await fsp.mkdir(dir, { recursive: true })
+  await fsp.writeFile(summaryFile(workspaceRoot), `${JSON.stringify(map, null, 2)}\n`, 'utf8')
+}
+
+/** 读某工单全部已生成的文件说明：`{ [path]: summary }`。无则空对象。 */
+export async function readFileSummaries(
+  workspaceRoot: string,
+  issueNumber: number,
+): Promise<Record<string, string>> {
+  const map = await readMap(workspaceRoot)
+  const prefix = `sum:${issueNumber}:`
+  const out: Record<string, string> = {}
+  for (const [k, v] of Object.entries(map)) {
+    if (k.startsWith(prefix))
+      out[k.slice(prefix.length)] = v
+  }
+  return out
+}
+
+/** 写某文件的说明。空串则删除该 key。 */
+export async function writeFileSummary(
+  workspaceRoot: string,
+  issueNumber: number,
+  filePath: string,
+  summary: string,
+): Promise<void> {
+  const map = await readMap(workspaceRoot)
+  const key = summaryKey(issueNumber, filePath)
+  if (summary.length > 0)
+    map[key] = summary
+  else
+    delete map[key]
+  await writeMap(workspaceRoot, map)
+}
+
+/** 读某工单最近一次生成会话的 sessionId；无则 undefined。 */
+export async function readSummarySession(
+  workspaceRoot: string,
+  issueNumber: number,
+): Promise<string | undefined> {
+  const map = await readMap(workspaceRoot)
+  return map[sessionKey(issueNumber)] || undefined
+}
+
+/** 写某工单续会话 sessionId。传 undefined / 空串则删除（下次从头开会话）。 */
+export async function writeSummarySession(
+  workspaceRoot: string,
+  issueNumber: number,
+  sessionId: string | undefined,
+): Promise<void> {
+  const map = await readMap(workspaceRoot)
+  const key = sessionKey(issueNumber)
+  if (sessionId && sessionId.length > 0)
+    map[key] = sessionId
+  else
+    delete map[key]
+  await writeMap(workspaceRoot, map)
+}