feat(WARDEN-WP-0021): T1+T2 — scheduled worker tick enabled (systemd --user timer)

T1: systemd --user units (ops-warden-worker.{service,timer}) + scripts/install-worker-timer.sh
(--enable opt-in, cron fallback documented) + examples/worker.env.example. Kill switch:
`systemctl --user disable --now ops-warden-worker.timer` or WORKER_ENABLED=0. Installed and
ENABLED — verified a real systemd run (Result=success, used the llm brain) and the timer is
active (next run +15min).

T2: hardened worker-tick.sh — State Hub /state/health precheck → graceful skip (exit 0) when
unreachable; worker-run failure logged but never fails the unit (retry next tick). Verified
hub-down skip and a live tick.

Conservative tier only; nothing auto-sent. Kill switch is one command.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

systemd/ops-warden-worker.service

@@ -0,0 +1,14 @@
+[Unit]
+Description=ops-warden conservative coordination worker (one tick)
+Documentation=https://gitea.coulomb.social/coulomb/ops-warden
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+# uv lives in ~/.local/bin; kubectl in /usr/local/bin or /usr/bin.
+Environment=PATH=%h/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+EnvironmentFile=%h/.config/warden/worker.env
+ExecStart=@ROOT@/scripts/worker-tick.sh
+# A graceful skip (hub down, WORKER_ENABLED=0) exits 0; never restart-loop.
+TimeoutStartSec=180