refactor: 拆分 3 个过大 ACP 文件为模块化子文件（每个 <500 行）

通过 4 阶段 workflow（分析 → 计划 → 重构 → 验证）将 3 个超大的 ACP
源文件拆分为 28 个模块化子文件，每个均严格小于 500 行，且完整保留
所有公共 API（barrel 模式重导出）。

变更概要：
- packages/acp-link/src/server.ts: 1800 → 20 行（barrel），新增 11 个子模块
  （server/types、payload-decode、permission-mode、runtime-state、dispatch、
  handlers-agent、handlers-session、acp-client、client-send、start-server、
  testing-internals）
- src/services/acp/agent.ts: 1297 → 33 行（barrel），新增 9 个子模块
  （agent/AcpAgent、sessionTypes、permissionMode、configOptions、promptQueue、
  internalAccessors、createSessionMethod、sessionLifecycle、promptFlow）
- src/services/acp/bridge.ts: 1516 → 29 行（barrel），新增 8 个子模块
  （bridge/types、paths、contentBlocks、toolInfo、toolResults、modelUsage、
  notifications、forwarding）

验证：
- bun run precheck 全通过（typecheck + lint + 5851 tests）
- ACP service tests: 176 pass / 0 fail
- ACP link tests: 47 pass / 0 fail
- 所有外部消费者（entry.ts、permissions.ts、__tests__/）的 import 路径不变
- 测试文件零修改

迁移计划详见 docs/acp-refactor-plan.md。

Co-Authored-By: glm-5.2 <zai-org@claude-code-best.win>

src/services/acp/agent/promptFlow.ts

@@ -0,0 +1,293 @@
+/**
+ * Prompt-flow methods for AcpAgent, attached to the prototype via
+ * Object.assign. Kept in a sibling module to keep AcpAgent.ts under the
+ * 500-line budget. The barrel (./index.ts) imports this module for its
+ * side effect so the prototype is populated before any instance is built.
+ *
+ * Methods attached: prompt, setSessionConfigOption.
+ */
+import { randomUUID } from 'node:crypto'
+import type {
+  PromptRequest,
+  PromptResponse,
+  SetSessionConfigOptionRequest,
+  SetSessionConfigOptionResponse,
+} from '@agentclientprotocol/sdk'
+import type { SessionId } from '../../../types/ids.js'
+import {
+  switchSession,
+  getSessionProjectDir,
+} from '../../../bootstrap/state.js'
+import { forwardSessionUpdates } from '../bridge.js'
+import type { ToolUseCache } from '../bridge.js'
+import { promptToQueryInput } from '../promptConversion.js'
+import { sanitizeTitle } from '../utils.js'
+import { AcpAgent } from './AcpAgent.js'
+import type { AcpSession } from './sessionTypes.js'
+import { flattenConfigOptionValues } from './configOptions.js'
+import { popNextPendingPrompt } from './promptQueue.js'
+import {
+  getConnection,
+  readClientCapabilities,
+  syncSessionConfigState,
+} from './internalAccessors.js'
+
+// ── prompt ───────────────────────────────────────────────────────
+
+async function prompt(
+  this: AcpAgent,
+  params: PromptRequest,
+): Promise<PromptResponse> {
+  const session = this.sessions.get(params.sessionId)
+  if (!session) {
+    throw new Error(`Session ${params.sessionId} not found`)
+  }
+
+  // Extract text/image content from the prompt
+  const promptInput = promptToQueryInput(params.prompt)
+
+  // Per prompt-turn.mdx, `prompt` is a required ContentBlock[] and an
+  // effectively-empty prompt is malformed input — reject it with an
+  // invalid_params error rather than fabricating a successful end_turn.
+  if (!promptInput.trim()) {
+    throw new Error('Prompt content is empty')
+  }
+
+  const promptCancelGeneration = session.cancelGeneration
+
+  // Handle prompt queuing — if a prompt is already running, queue this one
+  if (session.promptRunning) {
+    const promptUuid = randomUUID()
+    const cancelled = await new Promise<boolean>(resolve => {
+      session.pendingQueue.push(promptUuid)
+      session.pendingMessages.set(promptUuid, { resolve })
+    })
+    if (cancelled) {
+      return { stopReason: 'cancelled' }
+    }
+  }
+
+  if (session.cancelGeneration !== promptCancelGeneration) {
+    return { stopReason: 'cancelled' }
+  }
+
+  // Reset cancellation only when this prompt is about to run. Queued prompts
+  // must not clear the cancellation state for the active prompt.
+  session.cancelled = false
+  session.promptRunning = true
+
+  try {
+    // Reset the query engine's abort controller for a fresh query.
+    // After a previous interrupt(), the internal controller is stuck in
+    // aborted state — without this, submitMessage() fails immediately.
+    session.queryEngine.resetAbortController()
+    // Switch global session state so recordTranscript writes to the correct
+    // session file. Without this, multi-session scenarios (or creating a new
+    // session after another) write transcript data to the wrong file.
+    switchSession(params.sessionId as SessionId, getSessionProjectDir())
+
+    const sdkMessages = session.queryEngine.submitMessage(promptInput)
+
+    const { stopReason, usage } = await forwardSessionUpdates(
+      params.sessionId,
+      sdkMessages,
+      getConnection(this),
+      session.queryEngine.getAbortSignal(),
+      session.toolUseCache,
+      readClientCapabilities(this),
+      session.cwd,
+      () => session.cancelled,
+    )
+
+    // If the session was cancelled during processing, return cancelled
+    if (session.cancelled) {
+      return { stopReason: 'cancelled' }
+    }
+
+    // Emit a session_info_update so Clients learn the session's display
+    // title / last-activity timestamp via the stable v1 session/update
+    // channel. The title is derived from the first user prompt.
+    await emitSessionInfoUpdate(this, params.sessionId, promptInput)
+
+    // Per extensibility.mdx:39 the root of PromptResponse is reserved —
+    // stable v1 defines only `stopReason` (+ optional `_meta`). Token usage
+    // is therefore carried under the `_meta.claudeCode.usage` extension
+    // namespace rather than as a non-spec root field. thoughtTokens are
+    // included in totalTokens so reported totals match billable tokens;
+    // until bridge.ts tracks them they are reported as 0.
+    if (usage) {
+      const thoughtTokens = 0
+      return {
+        stopReason,
+        _meta: {
+          claudeCode: {
+            usage: {
+              inputTokens: usage.inputTokens,
+              outputTokens: usage.outputTokens,
+              cachedReadTokens: usage.cachedReadTokens,
+              cachedWriteTokens: usage.cachedWriteTokens,
+              thoughtTokens,
+              totalTokens:
+                usage.inputTokens +
+                usage.outputTokens +
+                usage.cachedReadTokens +
+                usage.cachedWriteTokens +
+                thoughtTokens,
+            },
+          },
+        },
+      }
+    }
+    return { stopReason }
+  } catch (err: unknown) {
+    // Treat AbortError / cancellation-shaped errors as a turn cancellation
+    // regardless of the session.cancelled flag, to close the race window
+    // between interrupt() firing and cancel() setting the flag. Per
+    // prompt-turn.mdx the Agent MUST return `cancelled` for aborts.
+    const isAbort =
+      err instanceof Error &&
+      (err.name === 'AbortError' ||
+        /abort|cancelled|interrupt/i.test(err.message))
+    if (session.cancelled || isAbort) {
+      return { stopReason: 'cancelled' }
+    }
+
+    // Check for process death errors
+    if (
+      err instanceof Error &&
+      (err.message.includes('terminated') ||
+        err.message.includes('process exited'))
+    ) {
+      await this.teardownSession(params.sessionId)
+      throw new Error(
+        'The Claude Agent process exited unexpectedly. Please start a new session.',
+      )
+    }
+
+    throw err
+  } finally {
+    // Resolve next pending prompt if any
+    const nextPrompt = popNextPendingPrompt(session)
+    if (nextPrompt) {
+      session.promptRunning = true
+      nextPrompt.resolve(false)
+    } else {
+      session.promptRunning = false
+    }
+  }
+}
+
+// ── setSessionConfigOption ───────────────────────────────────────
+
+async function setSessionConfigOption(
+  this: AcpAgent,
+  params: SetSessionConfigOptionRequest,
+): Promise<SetSessionConfigOptionResponse> {
+  const session = this.sessions.get(params.sessionId)
+  if (!session) {
+    throw new Error('Session not found')
+  }
+  if (typeof params.value !== 'string') {
+    throw new Error(
+      `Invalid value for config option ${params.configId}: ${String(params.value)}`,
+    )
+  }
+
+  const option = session.configOptions.find(o => o.id === params.configId)
+  if (!option) {
+    throw new Error(`Unknown config option: ${params.configId}`)
+  }
+
+  // Per session-config-options.mdx: value MUST be one of the values listed
+  // in the option's options array. Reject unknown values with an error
+  // rather than silently persisting them. Only `select` options carry an
+  // options array; `boolean` options have no enumerated values.
+  if (option.type === 'select') {
+    const validValues = flattenConfigOptionValues(
+      (option as { options?: unknown }).options,
+    )
+    if (!validValues.includes(params.value)) {
+      throw new Error(
+        `Invalid value '${params.value}' for config option ${params.configId}; must be one of: ${validValues.join(', ')}`,
+      )
+    }
+  }
+
+  const value = params.value
+
+  if (params.configId === 'mode') {
+    this.applySessionMode(params.sessionId, value)
+    await getConnection(this).sessionUpdate({
+      sessionId: params.sessionId,
+      update: {
+        sessionUpdate: 'current_mode_update',
+        currentModeId: value,
+      },
+    })
+  } else if (params.configId === 'model') {
+    session.queryEngine.setModel(value)
+  }
+
+  syncSessionConfigState(this, session, params.configId, value)
+
+  session.configOptions = session.configOptions.map(o =>
+    o.id === params.configId && typeof o.currentValue === 'string'
+      ? { ...o, currentValue: value }
+      : o,
+  )
+
+  return { configOptions: session.configOptions }
+}
+
+// ── Private-field accessors ──────────────────────────────────────
+//
+// getConnection / readClientCapabilities / syncSessionConfigState are
+// imported from ./internalAccessors.js (shared with sessionLifecycle.ts and
+// createSessionMethod.ts). The session_info_update helper below is local to
+// this module because it is only called from prompt().
+
+/**
+ * Emit a session_info_update notification carrying a derived session title
+ * (truncated first user prompt) and the current last-activity timestamp.
+ * Sent once per session — subsequent turns reuse the same title.
+ *
+ * This logic was originally the private `AcpAgent.maybeEmitSessionInfoUpdate`
+ * method on the shell class. It is only called from the prompt flow, so it
+ * lives here to avoid the `noUnusedPrivateClassMembers` false positive that
+ * cast-based access would otherwise trigger on the shell.
+ */
+async function emitSessionInfoUpdate(
+  agent: AcpAgent,
+  sessionId: string,
+  firstPrompt: string,
+): Promise<void> {
+  const session = agent.sessions.get(sessionId)
+  if (!session) return
+  // sessionInfoTitleSent is tracked via toolUseCache to avoid reshaping
+  // AcpSession; use a dedicated per-session flag instead.
+  const cache = session.toolUseCache as ToolUseCache & {
+    __sessionInfoTitleSent?: boolean
+  }
+  if (cache.__sessionInfoTitleSent) return
+  cache.__sessionInfoTitleSent = true
+  const title = sanitizeTitle(firstPrompt).slice(0, 100)
+  try {
+    await getConnection(agent).sessionUpdate({
+      sessionId,
+      update: {
+        sessionUpdate: 'session_info_update',
+        ...(title ? { title } : {}),
+        updatedAt: new Date().toISOString(),
+      },
+    })
+  } catch (err) {
+    console.error('[ACP] Failed to send session_info_update:', err)
+  }
+}
+
+// ── Prototype attachment ─────────────────────────────────────────
+
+Object.assign(AcpAgent.prototype, {
+  prompt,
+  setSessionConfigOption,
+})