refactor: deduplicate logger into shared module (#39)

three files created identical pino logger instances with the same config.
extract into src/logger.ts and import from each consumer.

net -9 lines, no behavior change.

Co-authored-by: ejae <ejae_dev@ejaes-Mac-mini.home>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

src/container-runner.ts

@@ -6,7 +6,6 @@ import { spawn } from 'child_process';
 import fs from 'fs';
 import os from 'os';
 import path from 'path';
-import pino from 'pino';
 
 import {
   CONTAINER_IMAGE,
@@ -15,14 +14,10 @@ import {
   DATA_DIR,
   GROUPS_DIR,
 } from './config.js';
+import { logger } from './logger.js';
 import { validateAdditionalMounts } from './mount-security.js';
 import { RegisteredGroup } from './types.js';
 
-const logger = pino({
-  level: process.env.LOG_LEVEL || 'info',
-  transport: { target: 'pino-pretty', options: { colorize: true } },
-});
-
 // Sentinel markers for robust output parsing (must match agent-runner)
 const OUTPUT_START_MARKER = '---NANOCLAW_OUTPUT_START---';
 const OUTPUT_END_MARKER = '---NANOCLAW_OUTPUT_END---';