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/permissionMode.ts

@@ -0,0 +1,115 @@
+import type { PermissionMode } from '../../../types/permissions.js'
+import { resolvePermissionMode } from '../utils.js'
+
+export const permissionModeIds: readonly PermissionMode[] = [
+  'auto',
+  'default',
+  'acceptEdits',
+  'bypassPermissions',
+  'dontAsk',
+  'plan',
+]
+
+export function isPermissionMode(modeId: string): modeId is PermissionMode {
+  return (permissionModeIds as readonly string[]).includes(modeId)
+}
+
+export function resolveSessionPermissionMode(
+  metaMode: unknown,
+  hasMetaMode: boolean,
+  settingsMode: unknown,
+): PermissionMode {
+  if (hasMetaMode) {
+    const metaResolved = resolveRequiredPermissionMode(
+      metaMode,
+      '_meta.permissionMode',
+    )
+    if (
+      metaResolved === 'bypassPermissions' &&
+      !isAcpBypassPermissionModeAvailable(settingsMode)
+    ) {
+      throw new Error(
+        'Mode not available: bypassPermissions requires a local ACP bypass opt-in.',
+      )
+    }
+
+    return metaResolved
+  }
+
+  const settingsResolved = resolveConfiguredPermissionMode(settingsMode)
+  return settingsResolved ?? 'default'
+}
+
+function resolveRequiredPermissionMode(
+  mode: unknown,
+  source: string,
+): PermissionMode {
+  if (mode === undefined || mode === null) {
+    throw new Error(`Invalid ${source}: expected a string.`)
+  }
+
+  return resolvePermissionMode(mode, source) as PermissionMode
+}
+
+function resolveConfiguredPermissionMode(
+  mode: unknown,
+): PermissionMode | undefined {
+  if (mode === undefined || mode === null) return undefined
+
+  try {
+    return resolvePermissionMode(
+      mode,
+      'permissions.defaultMode',
+    ) as PermissionMode
+  } catch (err: unknown) {
+    const reason = err instanceof Error ? err.message : String(err)
+    console.error(
+      '[ACP] Invalid permissions.defaultMode, using default:',
+      reason,
+    )
+    return undefined
+  }
+}
+
+export function hasOwnField(
+  value: Record<string, unknown> | null | undefined,
+  key: string,
+): boolean {
+  return !!value && Object.hasOwn(value, key)
+}
+
+export function isAcpBypassPermissionModeAvailable(
+  settingsMode?: unknown,
+): boolean {
+  return (
+    isProcessBypassPermissionModeAvailable() &&
+    (isAcpBypassLocallyEnabled() ||
+      isSettingsBypassPermissionMode(settingsMode))
+  )
+}
+
+function isProcessBypassPermissionModeAvailable(): boolean {
+  if (process.env.IS_SANDBOX) return true
+  if (typeof process.geteuid === 'function') return process.geteuid() !== 0
+  if (typeof process.getuid === 'function') return process.getuid() !== 0
+  return true
+}
+
+function isAcpBypassLocallyEnabled(): boolean {
+  return (
+    process.env.ACP_PERMISSION_MODE === 'bypassPermissions' ||
+    isTruthyEnv(process.env.CLAUDE_CODE_ACP_ALLOW_BYPASS_PERMISSIONS)
+  )
+}
+
+function isSettingsBypassPermissionMode(settingsMode: unknown): boolean {
+  try {
+    return resolvePermissionMode(settingsMode) === 'bypassPermissions'
+  } catch {
+    return false
+  }
+}
+
+function isTruthyEnv(value: string | undefined): boolean {
+  return value === '1' || value?.toLowerCase() === 'true'
+}