Add file-based locking (flock) for cross-process SQLite coordination.
Multiple hermes processes (gateway + CLI + worktree agents) share
one state.db but each had its own threading.Lock.
Changes:
- hermes_state_patch.py: CrossProcessLock class using flock()
- File-based locking for true cross-process coordination
- Increased retry parameters for cross-process contention
- Monkey-patch function for easy integration
Fixes: Issue #52 - SQLite global write lock causes contention
Refs: CWE-412: Unrestricted Externally Accessible Lock