- Add validateProjectPath() to reject sensitive system directories
- Add isPathWithinRoot/isPathWithinRootReal for symlink-aware path checks
- Replace hand-rolled glob-to-regex with picomatch to prevent ReDoS
- Add isSafeRegex() to reject custom patterns with nested quantifiers
- Replace FileLock with PID-tracking version that detects stale locks
- Add symlink detection in removeDirectory/listDirectoryContents
- Add subdirectory name validation in ensureSubdirectory
- Add atomicWriteFileSync and corrupted file backup in config-writer
- Add MCP input validation (validateString) for all tool handlers
- Fix CLAUDE.md section replacement to handle ### subsections correctly
