docs: update CLAUDE.md with file logging documentation #35

- Added detailed file logging information to Logger component section
- Documented file logging configuration options in Environment Configuration
- Added debugging section with log file location (/var/log/agent-manager.log)
- Mentioned automatic rotation and systemd auto-detection
- Added file logging to Important Patterns list

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

CLAUDE.md

@@ -67,8 +67,15 @@ index.js (Entry Point)
 - Exported as singleton
 
 **Logger (src/logger.js)**
-- Console-based logger with ANSI colors and timestamps
-- Methods: `info()`, `error()`, `webhook()`
+- Console and file-based logger with ANSI colors and timestamps
+- Methods: `info()`, `error()`, `webhook()`, `warn()`, `debug()`, `jobLifecycle()`
+- **File logging support** with automatic rotation:
+  - Enabled by default when running as systemd service
+  - Configurable via `FILE_LOGGING_ENABLED` environment variable
+  - Default log file: `/var/log/agent-manager.log`
+  - Automatic rotation when file reaches `MAX_LOG_SIZE` (default: 10MB)
+  - Keeps up to `MAX_LOG_FILES` rotated files (default: 5)
+  - ANSI color codes stripped from file output
 - Exported as singleton
 
 **EmailNotifier (src/emailNotifier.js)**
@@ -134,6 +141,13 @@ sudo /bin/systemctl status agent-manager
 sudo journalctl -u agent-manager -f
 ```
 
+**View application log file:**
+```bash
+tail -f /var/log/agent-manager.log
+```
+
+**Debugging**: When running as a systemd service, file logging is enabled by default. All application logs (INFO, WARN, ERROR, DEBUG, webhook events, job lifecycle) are written to `/var/log/agent-manager.log`. The log file is automatically rotated when it reaches 10MB (default), keeping up to 5 rotated files. For troubleshooting issues, check this file for detailed execution logs.
+
 **Note**: The `claude` user has passwordless sudo access to restart the agent-manager service via `/etc/sudoers.d/50-agent-manager` configuration.
 
 **Testing endpoints:**
@@ -170,6 +184,16 @@ WEBHOOK_{EVENT_TYPE}_ENABLED=true|false
 
 **Supported Event Types:** push, pull_request, create, delete, release, issues, issue_comment, global
 
+**File Logging Configuration:**
+```env
+FILE_LOGGING_ENABLED=true|false  # Enable/disable file logging (default: false, auto-enabled for systemd)
+LOG_FILE_PATH=/var/log/agent-manager.log  # Path to log file (default: /var/log/agent-manager.log)
+MAX_LOG_SIZE=10485760  # Max size in bytes before rotation (default: 10MB)
+MAX_LOG_FILES=5  # Number of rotated files to keep (default: 5)
+```
+
+**Note**: File logging is **automatically enabled** when running as a systemd service. The logger detects systemd environment and enables file output by default. For debugging, check `/var/log/agent-manager.log`.
+
 **MCP Server Configuration:**
 ```env
 GOGS_MCP_PATH=/data/gogs-mcp/dist/index.js  # Path to gogs-mcp server for headless Claude Code
@@ -239,6 +263,7 @@ Copy from `commands.json.example` and configure commands for each event type.
 9. **Multiple Commands**: Each event type can have multiple commands that execute sequentially
 10. **Shell & Node Execution**: Commands can be shell scripts or Node.js scripts
 11. **Email Notifications**: Optional callback-based email notifications with condition matching
+12. **File Logging**: Automatic file logging with rotation (enabled by default for systemd services)
 
 ## Extending with Callbacks