add startup circuit breaker and troubleshooting docs

Backs off on rapid restarts to avoid exhausting Discord gateway identify
limits and triggering Cloudflare IP bans. Resets on clean shutdown so only
crashes accumulate the counter. Also adds a troubleshooting section to
CLAUDE.md with the most useful diagnostic locations.

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

src/index.ts

@@ -7,6 +7,7 @@
 import path from 'path';
 
 import { DATA_DIR } from './config.js';
+import { enforceStartupBackoff, resetCircuitBreaker } from './circuit-breaker.js';
 import { migrateGroupsToClaudeLocal } from './claude-md-compose.js';
 import { initDb } from './db/connection.js';
 import { runMigrations } from './db/migrations/index.js';
@@ -58,6 +59,9 @@ import { initChannelAdapters, teardownChannelAdapters, getChannelAdapter } from
 async function main(): Promise<void> {
   log.info('NanoClaw starting');
 
+  // 0. Circuit breaker — backoff on rapid restarts
+  await enforceStartupBackoff();
+
   // 1. Init central DB
   const dbPath = path.join(DATA_DIR, 'v2.db');
   const db = initDb(dbPath);
@@ -175,6 +179,7 @@ async function shutdown(signal: string): Promise<void> {
   stopDeliveryPolls();
   stopHostSweep();
   await teardownChannelAdapters();
+  resetCircuitBreaker();
   process.exit(0);
 }