Implement REIN-A-0002 ops_run claim loop and approach registry.

Add activity-core ops_run client, approach selection (FI/Binky/mail/agent),
claim-loop worker with lease heartbeat, CLI run --from-ops-run and claim-loop,
install units, and docs demoting issue-core to legacy external tickets.
T05 timer cutover remains operator after five clean cycles.

deploy/systemd/rein-aharness-claim-loop.service

@@ -0,0 +1,22 @@
+[Unit]
+Description=rein-aharness ops_run claim loop (activity-core automation)
+Documentation=file:%h/rein-aharness/docs/ops-run-claim-loop.md
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+# Adjust paths for the railiance user checkout
+WorkingDirectory=%h/rein-aharness
+EnvironmentFile=-%h/.config/rein-aharness/claim-loop.env
+Environment=PYTHONUNBUFFERED=1
+# Prefer venv entrypoint when installed with uv/pip
+ExecStart=%h/rein-aharness/.venv/bin/rein-aharness claim-loop
+Restart=on-failure
+RestartSec=15
+# Soft stop: claim-loop handles SIGTERM between cycles
+KillSignal=SIGTERM
+TimeoutStopSec=120
+
+[Install]
+WantedBy=default.target