fix(modules): break circular import TDZ between index.ts and modules

PR #3 introduced a circular-import temporal-dead-zone bug that didn't
surface in unit tests but crashed the service at startup:

  src/index.ts imports './modules/index.js' for side effects
  → src/modules/interactive/index.ts calls registerResponseHandler()
  → that function is declared in src/index.ts
  → but src/index.ts's const responseHandlers = [] hasn't been
    initialized yet (we're in the middle of its module-init)
  → ReferenceError: Cannot access 'responseHandlers' before initialization

Same issue for registerResponseHandler itself (the function reference
resolves to undefined) and for onShutdown in the approvals module.

Caught when the operator started the service and systemd flagged the
process as crashing in auto-restart loop.

Fix: extract responseHandlers + registerResponseHandler + shutdownCallbacks
+ onShutdown into src/response-registry.ts, which has no dependencies on
src/index.ts or on modules. index.ts re-exports the same surface for any
existing consumers; modules import directly from response-registry.js.

The bug was latent because:
- Unit tests import pieces, never src/index.ts's main() flow.
- Host builds clean because TypeScript doesn't catch runtime circular
  init order.
- Only surfaces when the ES module loader actually executes src/index.ts
  as the entry point.

Verified: service boots on Linux host with approvals + interactive
loaded; OneCLI handler starts via onDeliveryAdapterReady callback.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/modules/approvals/index.ts

@@ -11,7 +11,7 @@
  *   - A shutdown callback that stops the OneCLI handler cleanly.
  */
 import { registerDeliveryAction, onDeliveryAdapterReady } from '../../delivery.js';
-import { registerResponseHandler, onShutdown } from '../../index.js';
+import { registerResponseHandler, onShutdown } from '../../response-registry.js';
 import { handleAddMcpServer, handleInstallPackages, handleRequestRebuild } from './request-approval.js';
 import { handleApprovalsResponse } from './response-handler.js';
 import { startOneCLIApprovalHandler, stopOneCLIApprovalHandler } from './onecli-approvals.js';

src/modules/approvals/response-handler.ts

@@ -16,7 +16,7 @@ import { updateContainerConfig } from '../../container-config.js';
 import { buildAgentGroupImage, killContainer, wakeContainer } from '../../container-runner.js';
 import { getAgentGroup } from '../../db/agent-groups.js';
 import { deletePendingApproval, getPendingApproval, getSession } from '../../db/sessions.js';
-import type { ResponsePayload } from '../../index.js';
+import type { ResponsePayload } from '../../response-registry.js';
 import { log } from '../../log.js';
 import { writeSessionMessage } from '../../session-manager.js';
 import type { PendingApproval } from '../../types.js';

src/modules/interactive/index.ts

@@ -13,7 +13,7 @@
 import { getDb, hasTable } from '../../db/connection.js';
 import { deletePendingQuestion, getPendingQuestion, getSession } from '../../db/sessions.js';
 import { wakeContainer } from '../../container-runner.js';
-import { registerResponseHandler, type ResponsePayload } from '../../index.js';
+import { registerResponseHandler, type ResponsePayload } from '../../response-registry.js';
 import { log } from '../../log.js';
 import { writeSessionMessage } from '../../session-manager.js';