telemetry: ci.job_cancelled from the janitor; interval_s on heartbeat

The janitor now returns one JSON line per job it cancels (repo, workflow,
job, reason, runs_on, waited_s) into a spool; the emitter ships them as
ci.job_cancelled (declared with Telemetry Boss) and truncates the spool
only after a 2xx. Run status recompute folded into the same statement.

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

scripts/cancel_unrunnable.sh

@@ -1,6 +1,10 @@
 #!/usr/bin/env bash
 # Cancel jobs no runner can ever take (see cancel_unrunnable.sql). Run on Veron as root.
 set -euo pipefail
-n=$(docker exec -i windy-git-db-1 sh -c 'psql -U "$POSTGRES_USER" -d gitea -At -v ON_ERROR_STOP=1' \
-      < "$(dirname "$0")/cancel_unrunnable.sql" | grep -cE '^[0-9]+$' || true)
-echo "[janitor] cancelled unrunnable jobs in ${n} run(s)"
+SPOOL="${JANITOR_SPOOL:-/var/lib/windy-git/janitor-cancelled.jsonl}"
+mkdir -p "$(dirname "$SPOOL")"
+out=$(docker exec -i windy-git-db-1 sh -c 'psql -U "$POSTGRES_USER" -d gitea -At -v ON_ERROR_STOP=1' \
+        < "$(dirname "$0")/cancel_unrunnable.sql")
+printf '%s\n' "$out" | grep '^{' >> "$SPOOL" || true
+n=$(printf '%s\n' "$out" | grep -c '^{' || true)
+echo "[janitor] cancelled ${n} unrunnable job(s)"