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>

packages/acp-link/src/server/acp-client.ts

@@ -0,0 +1,102 @@
+import type { WSContext } from 'hono/ws'
+import * as acp from '@agentclientprotocol/sdk'
+import { send } from './client-send.js'
+import {
+  PERMISSION_TIMEOUT_MS,
+  generateRequestId,
+  logPerm,
+  logWs,
+} from './runtime-state.js'
+import { clients } from './runtime-state.js'
+import type { ClientState } from './types.js'
+
+// Create a Client implementation that forwards events to WebSocket
+export function createClient(
+  ws: WSContext,
+  clientState: ClientState,
+): acp.Client {
+  return {
+    async requestPermission(params) {
+      const requestId = generateRequestId()
+      logPerm.debug({ requestId, title: params.toolCall.title }, 'requested')
+
+      const outcomePromise = new Promise<
+        { outcome: 'cancelled' } | { outcome: 'selected'; optionId: string }
+      >(resolve => {
+        const timeout = setTimeout(() => {
+          logPerm.warn({ requestId }, 'timed out')
+          clientState.pendingPermissions.delete(requestId)
+          resolve({ outcome: 'cancelled' })
+        }, PERMISSION_TIMEOUT_MS)
+
+        clientState.pendingPermissions.set(requestId, { resolve, timeout })
+      })
+
+      send(ws, 'permission_request', {
+        requestId,
+        sessionId: params.sessionId,
+        options: params.options,
+        toolCall: params.toolCall,
+      })
+
+      const outcome = await outcomePromise
+      logPerm.debug({ requestId, outcome: outcome.outcome }, 'resolved')
+
+      return { outcome }
+    },
+
+    async sessionUpdate(params) {
+      send(ws, 'session_update', params)
+    },
+
+    async readTextFile(params) {
+      logWs.debug({ path: params.path }, 'readTextFile')
+      return { content: '' }
+    },
+
+    async writeTextFile(params) {
+      logWs.debug({ path: params.path }, 'writeTextFile')
+      return {}
+    },
+  }
+}
+
+// Handle permission response from client
+export function handlePermissionResponse(
+  ws: WSContext,
+  payload: {
+    requestId: string
+    outcome:
+      | { outcome: 'cancelled' }
+      | { outcome: 'selected'; optionId: string }
+  },
+): void {
+  const state = clients.get(ws)
+  if (!state) {
+    logPerm.warn('response from unknown client')
+    return
+  }
+
+  const pending = state.pendingPermissions.get(payload.requestId)
+  if (!pending) {
+    logPerm.warn(
+      { requestId: payload.requestId },
+      'response for unknown request',
+    )
+    return
+  }
+
+  clearTimeout(pending.timeout)
+  state.pendingPermissions.delete(payload.requestId)
+  pending.resolve(payload.outcome)
+}
+
+// Cancel all pending permissions for a client (called on disconnect)
+export function cancelPendingPermissions(clientState: ClientState): void {
+  for (const [requestId, pending] of clientState.pendingPermissions) {
+    logPerm.debug({ requestId }, 'cancelled on disconnect')
+    clearTimeout(pending.timeout)
+    pending.resolve({ outcome: 'cancelled' })
+  }
+  clientState.pendingPermissions.clear()
+}