forgejo-runner: convert to a role, de-Uptime-Kuma the health check

409-line playbook becomes a 16-line playbook plus a 318-line role with phases
split across tasks/{prerequisites,install,configure,service,healthcheck}.yml and
four templates. forgejo_runner_vars.yml is deleted; its content is the role's
defaults.

Applies the Plan 6 Stage 0 decision: keep whatever determines whether the
service is healthy, drop the Uptime Kuma specifics, make the reporting point
pluggable. Gone from the role: the embedded Python that created monitors over
the Kuma API, the /tmp credentials file, token extraction, the systemd
Environment= rewrite, and 8 `when: uptime_kuma_enabled` guards. What remains is
the check itself, its log, the systemd unit and timer, and an honest exit code -
`systemctl is-failed forgejo-runner-healthcheck.service` now answers the
question with no monitoring system involved at all.

Reporting is one variable, healthcheck_push_url, empty by default. Any endpoint
that accepts an HTTP ping plugs in there. A pull-based monitor wants it left
empty and reads unit state instead.

PREMISE CORRECTION: Uptime Kuma is NOT dead. Plan 3 recorded "48 push timers
curling an endpoint that no longer answers" and Plan 6 said the check had
"nowhere to report to". Both wrong - 24+ push scripts across 11 hosts are
pushing successfully right now (HTTP 200). Only the Ansible code and the vault
credentials were decommissioned; the service never stopped. So the existing push
URLs were harvested into a vaulted healthcheck_push_urls dict and are preserved,
keeping this refactor behaviour-neutral. Retiring Kuma stays a deliberate act
rather than a side effect. PLAN_3 and PLAN_6 are corrected.

Verified:
  - task-list diff vs the old playbook shows ONLY the five Kuma tasks removed,
    everything else identical and in the same order
  - first run ok=22 changed=1 (the rewritten health script); both systemd units
    and forgejo-runner.service came back ok, so the templates reproduce the
    previous files byte-for-byte
  - second run ok=22 changed=0, fully idempotent
  - still reports "Ping sent successfully (HTTP 200)" from a script containing
    zero Uptime Kuma references
  - the 4 skipped tasks are genuine already-configured guards, checked not assumed

Two things for the next service:

- import_tasks, not include_tasks. Dynamic includes are opaque to --list-tasks,
  which is the primary verification tool here; the first attempt produced a
  useless diff.
- `Assert runner is running` was guarded by uptime_kuma_enabled and so had not
  run since the decommissioning. It is not monitoring, it is the deployment
  checking its own work - the deprecation banner swept it up with the Kuma
  plumbing, and a runner that failed to start was deploying "successfully" in
  silence. Ungated now. The banner was applied to contiguous blocks, so read
  every uptime_kuma_enabled guard and ask whether it is monitoring or deployment.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ansible/roles/forgejo_runner/tasks/service.yml

@@ -0,0 +1,33 @@
+---
+- name: Create forgejo-runner systemd service
+  ansible.builtin.template:
+    src: forgejo-runner.service.j2
+    dest: /etc/systemd/system/forgejo-runner.service
+    owner: root
+    group: root
+    mode: '0644'
+
+- name: Reload systemd
+  systemd:
+    daemon_reload: yes
+
+- name: Enable and start forgejo-runner service
+  systemd:
+    name: forgejo-runner
+    enabled: yes
+    state: started
+
+- name: Verify forgejo-runner is active
+  command: systemctl is-active forgejo-runner
+  register: runner_active
+  changed_when: false
+
+# Ungated on purpose. This was previously guarded by `uptime_kuma_enabled`, but
+# it is not a monitoring task — it is the deployment asserting its own success.
+# The deprecation banner swept it up along with the Kuma plumbing, which meant a
+# broken runner deployed "successfully" and silently.
+- name: Assert runner is running
+  assert:
+    that:
+      - runner_active.stdout == "active"
+    fail_msg: "forgejo-runner service is not active: {{ runner_active.stdout }}"