fix(acp): 对齐 ACP session ID 与全局会话状态

在 newSession/resumeSession/loadSession 中调用 switchSession，
确保 transcript 持久化、analytics 与 cost tracking 使用 ACP session ID，
而非内部默认 session ID。

- newSession 生成 sessionId 后立即对齐全局状态
- resumeSession 命中 fingerprint 缓存路径也对齐
- loadSession 在 sessionIdExists() 检查前对齐（lookup 依赖 getSessionId）
- 补充 5 个测试覆盖上述路径，以及 prompt 不触发额外 switchSession

src/services/acp/agent.ts

@@ -53,7 +53,8 @@ import { getEmptyToolPermissionContext } from '../../Tool.js'
 import type { PermissionMode } from '../../types/permissions.js'
 import type { Command } from '../../types/command.js'
 import { getCommands } from '../../commands.js'
-import { setOriginalCwd } from '../../bootstrap/state.js'
+import { setOriginalCwd, switchSession } from '../../bootstrap/state.js'
+import type { SessionId } from '../../types/ids.js'
 import { enableConfigs } from '../../utils/config.js'
 import { FileStateCache } from '../../utils/fileStateCache.js'
 import { getDefaultAppState } from '../../state/AppStateStore.js'
@@ -471,6 +472,10 @@ export class AcpAgent implements Agent {
     const sessionId = opts.sessionId ?? randomUUID()
     const cwd = params.cwd
 
+    // Align the global session state so that transcript persistence,
+    // analytics, and cost tracking use the ACP session ID.
+    switchSession(sessionId as SessionId)
+
     // Set CWD for the session
     setOriginalCwd(cwd)
     const previousProcessCwd = process.cwd()
@@ -675,6 +680,8 @@ export class AcpAgent implements Agent {
           | undefined,
       })
       if (fingerprint === existingSession.sessionFingerprint) {
+        // Align global state so subsequent operations use the correct session
+        switchSession(params.sessionId as SessionId)
         return {
           sessionId: params.sessionId,
           modes: existingSession.modes,
@@ -687,6 +694,10 @@ export class AcpAgent implements Agent {
       await this.teardownSession(params.sessionId)
     }
 
+    // Align global state BEFORE sessionIdExists() check — the lookup uses
+    // getSessionId() internally when resolving project-scoped paths.
+    switchSession(params.sessionId as SessionId)
+
     // Set CWD early so session file lookup can find the right project directory
     setOriginalCwd(params.cwd)