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/api/anthropic-proxy.ts

@@ -6,8 +6,8 @@ const ANTHROPIC_API_BASE = 'https://api.anthropic.com';
 const CREDENTIALS_PATH = join(homedir(), '.claude', '.credentials.json');
 
 // Generate a random proxy secret at startup — shared with Claude Code spawns
-// Prefix with sk-ant- so Claude Code accepts it as a valid API key format
-export const proxySecret = `sk-ant-proxy01-${crypto.randomUUID()}`;
+// Prefix must match a real Anthropic API key format (sk-ant-api03-*) so Claude Code accepts it
+export const proxySecret = `sk-ant-api03-${crypto.randomUUID()}`;
 
 type CredentialsFile = {
   claudeAiOauth?: {