Scheduled-loop infra: lockfile guard + release + fire log

- scripts/loop-guard.sh — atomic claim with 30-min staleness overtake,
  appends NDJSON event to .loop-logs/<lang>.ndjson. Exit 0 = go ahead,
  exit 1 = another run is live, skip.
- scripts/loop-release.sh — clear lock, log release with exit status.

Intended for 7 per-language /schedule routines firing every 15 minutes.
Lock detects overlap so tight cadences are safe; stale lock (>30 min)
overtaken automatically if an agent dies mid-run.

scripts/loop-release.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+LANG=${1:?usage: loop-release.sh <lang>}
+STATUS=${2:-done}
+ROOT=$(cd "$(dirname "$0")/.." && pwd)
+cd "$ROOT"
+LOCK=".loop-locks/$LANG.claim"
+LOG=".loop-logs/$LANG.ndjson"
+ISO=$(date -Iseconds)
+rm -f "$LOCK"
+printf '{"ts":"%s","lang":"%s","status":"released","exit":"%s"}\n' "$ISO" "$LANG" "$STATUS" >> "$LOG"
+echo "OK: $LANG released ($STATUS)"