feat: dark factory — autonomous CI/CD agents for harb

Three agents extracted from ~/scripts/harb-{dev,review}/:

- dev/ — pull-based dev agent (find ready issues → implement → PR → merge)
- review/ — AI code review (structured verdicts, follow-up issues)
- factory/ — supervisor (bash health checks, auto-fix, escalation)

All secrets externalized to .env (see .env.example).
Shared env/helpers in lib/env.sh.

.gitignore

@@ -0,0 +1,11 @@
+# Secrets
+.env
+
+# Runtime state
+*.log
+state.json
+*.lock
+*.pid
+
+# OS
+.DS_Store