process sidecar: independent process manager for long-running work

Introduces a separate Bun process (port 5100) that owns all spawned
processes and long-running work, so the API server can restart freely
without disrupting active sessions.

The sidecar owns:
- Anthropic proxy (port 5051) with persisted secret across restarts
- Claude Code process spawning and session tracking (--resume support)
- Pi agent spawning and RPC lifecycle (prompt/abort/thinking)
- Job queue engine (lane processing, retries, notifications)

The API server becomes a thin client that forwards commands over a
single WebSocket connection with auto-reconnect. send-claude-code.ts
goes from 550 lines of spawn logic to 73 lines of sidecar delegation.

State persisted to data/sidecar/state.json every 30s and on shutdown.
Lockfile prevents duplicate instances. See SIDECAR.md for full docs
and manual testing procedures.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/servers/channels/whatsapp/handler.ts

@@ -4,7 +4,7 @@ import { sendAndAwait, getSessionModel, setSessionModel } from '../send-and-awai
 import { consumePairingCode } from '../pairing';
 import { getWhatsAppClient } from './bot';
 import { listPiModels } from '@@/api/pi/list-models';
-import { enqueue } from '@@/queue/engine';
+import { enqueueJob } from '../../sidecar-client';
 import { readJob } from '@@/queue/storage';
 import { openEmailDb } from '@@/api/email/email-db';
 import type { ModelInfo } from '@@/api/pi/types';
@@ -64,7 +64,7 @@ async function handleEmailSync(ctx: CommandContext): Promise<void> {
 
   await send('Syncing emails...');
 
-  const job = await enqueue({ lane: 'google-api', type: 'gmail-sync', userId: email });
+  const job = await enqueueJob({ lane: 'google-api', type: 'gmail-sync', userId: email });
 
   const poll = async (): Promise<'completed' | 'failed' | 'cancelled'> => {
     for (let i = 0; i < 120; i++) {