- update the watcher start helper to remove the old /tmp/<build-name>.log file before starting a fresh watcher instance for a reused build name
- prevent the watcher from inheriting stale started_at timestamps from previous runs with the same build name and immediately exiting as HUNG
- make reused-build watcher startup safer by resetting both watcher state and the matching temporary runner log
- update the watcher start helper to stop any stale watcher instance for the same requested parent build name and remove its old state directory before starting fresh
- document that reused parent build names must not inherit stale cancelled, posted, state.json, or subruns state from older runs
- update the watcher install and design docs so the controller workflow explicitly treats stale reused-build-name state as part of startup cleanup
- update the watcher design and automation guide to treat --categorize as sequential ATVM sub-runs rather than one parent run with internal phases
- document that categorized runs should send one Mattermost status per completed grouped sub-run instead of one parent-only final post
- add a --categorize option to the watcher start helper so categorized mode is explicit in watcher startup
- update the watcher implementation to track categorized sub-runs separately, write per-subrun state, and post each completed grouped run once
- add the per-run ATVM watcher service package under atvm/watcher-service, including the Python watcher, systemd template unit, helper scripts, and deployment docs
- document the watcher-service install and operating model, including one-run-per-instance behavior, Mattermost posting rules, and the best-practice /opt/atvm-watcher-service install path
- clarify ATVM run approval semantics so `approve` means run without watcher and `approve with watcher` means run and start the watcher
- update the ATVM automation guide and AGENTS rules so watcher usage and approval behavior are explicit and consistent
