feat: add crg-daemon multi-repo watch daemon

[imkarrer]

Summary

Adds a multi-repo watch daemon (crg-daemon) that spawns child processes (subprocess.Popen) each running code-review-graph watch for a configured repository. The daemon reads its configuration from a TOML file, monitors it for live changes, health-checks running watchers, and auto-restarts dead ones. No external dependencies (no tmux, no screen) — pure Python stdlib process management.

Motivation

The graph can go stale when changes occur outside agent-driven updates — manual edits, branch switches, rebases, or pulls from teammates. The daemon orchestrates watchers automatically across configured repos so the graph stays current without relying on hooks or manual rebuilds.

Related: #36, #59.

Changes

New files

File	Lines	Description
code_review_graph/daemon.py	~950	Core daemon: DaemonConfig/WatchRepo dataclasses, TOML load/save, ConfigWatcher, WatchDaemon (start/stop/reconcile/daemonize/health-check/run_forever), PID management, subprocess.Popen child process management with threading.Lock, persisted state file (daemon-state.json) for cross-process status queries
code_review_graph/daemon_cli.py	~330	Standalone crg-daemon argparse CLI with 7 subcommands: start, stop, restart, status, logs, add, remove; status reads persisted state to report live/dead watchers
tests/test_daemon.py	~940	40 tests covering config parsing, PID management, WatchDaemon lifecycle, health checking with auto-restart, reconciliation (including auto-build and registry registration), state persistence, cross-process status reporting, and CLI handlers

Modified files

File	Description
code_review_graph/cli.py	Added daemon subparser group with 7 subcommands delegating to daemon_cli handlers; updated module docstring
pyproject.toml	Added crg-daemon entry point in [project.scripts]; added tomli conditional dependency for Python < 3.11
README.md	Added "Multi-repo daemon" to Features table, CLI reference, and new expandable details section
docs/COMMANDS.md	Added daemon CLI commands and standalone crg-daemon reference with config example
docs/ROADMAP.md	Added v2.2.0 section under Shipped

How it works

1. User defines repos in ~/.code-review-graph/watch.toml
2. crg-daemon start spawns one subprocess.Popen child per repo, each running code-review-graph watch with stdout/stderr redirected to per-repo log files
3. A background thread monitors watch.toml for changes and reconciles child processes (starts new repos, terminates removed ones)
4. On reconciliation, new repos are automatically registered in the central registry and their graphs are built if graph.db does not yet exist — no manual code-review-graph build needed
5. Health checks run every 30 seconds — dead watchers (detected via proc.poll()) are automatically restarted
6. crg-daemon start (without --foreground) double-forks to daemonize, writing a PID file for lifecycle management
7. _terminate_child() sends SIGTERM, waits up to 5 seconds, then escalates to SIGKILL
8. Thread-safe access to _children: dict[str, Popen] via threading.Lock
9. Cross-process status: daemon persists child PIDs to daemon-state.json on every mutation; crg-daemon status reads this file and probes PIDs with os.kill(pid, 0) to report alive/dead without needing the daemon object in-memory

Usage

# Add repos
crg-daemon add ~/project-a --alias proj-a
crg-daemon add ~/project-b

# Start daemon
crg-daemon start

# Check status
crg-daemon status

# View logs
crg-daemon logs --repo proj-a -f

# Add a new repo while daemon is running — graph is built automatically
crg-daemon add ~/project-c --alias proj-c

# Stop
crg-daemon stop

Also available as code-review-graph daemon start|stop|status|....

Testing

• 40 tests in tests/test_daemon.py
• All tests pass: uv run pytest tests/test_daemon.py -v
• Ruff: clean
• Mypy: no new errors (3 pre-existing unrelated issues in cli.py)

Checklist

• Feature branch from main
• Tests added for new functionality (40 tests)
• All tests pass (uv run pytest)
• Linting passes (uv run ruff check code_review_graph/)
• Documentation updated (README, COMMANDS.md, ROADMAP.md)
• No breaking changes to existing CLI or MCP tools
• No external dependencies (pure stdlib subprocess management)
• Code style: 100-char lines, Python 3.10+, from __future__ import annotations, type hints, logging.getLogger(__name__), no shell=True, parameterized SQL
• Cross-process status reporting via persisted state file
• reconcile() auto-builds graphs and registers new repos (parity with start())