fix(ansible): git sources work in the image and survive a redeploy; pulls time out; alert vars go in a JSON file (#5157)

- git ships in the image; checkouts live under /data/ansible/sources
  (STEWARD_ANSIBLE_SOURCE_DIR), on the persistent volume.
- One task, ansible_git_pulls, reads the sources every 30 s and pulls each
  as its interval passes: a source added in Settings is pulled without a
  restart, a removed one is forgotten.
- git_pull: a 120 s timeout ending the process group, GIT_TERMINAL_PROMPT=0,
  pull --ff-only, a failed clone removed; it raises GitPullError with git's
  message, so the Sync button stops saying Synced after a failure (and the
  message is now escaped).
- An alert action's vars and the firing's steward_alert_* vars reach
  ansible-playbook as one JSON extra-vars file, not -e key=value, which
  Ansible split on whitespace (a rule named 'High CPU on web').

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/core/ansible.md

@@ -31,10 +31,9 @@ ansible.sources:
     url: "https://github.com/example/infra.git"
     branch: "main"
     pull_interval_seconds: 300
-    cache_path: "/data/playbook_cache/infra-repo"
 ```
 
-Git sources register a `ScheduledTask` named `ansible_git_pull_<name>` that runs `git pull` on the configured interval.
+Each git source is checked out under `/data/ansible/sources/<name>` (override with `STEWARD_ANSIBLE_SOURCE_DIR`), on the persistent volume, so a redeploy keeps it. One scheduled task, `ansible_git_pulls`, ticks every 30 s and pulls each source once its `pull_interval_seconds` has passed; a source added in Settings is pulled within a tick, with no restart. A clone or pull that runs past 120 s is cut (its process group terminated), a clone that fails is removed so the next attempt starts clean, and git never prompts for credentials.
 
 ---