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.

.gitignore

@@ -29,3 +29,7 @@ test-case-define.txt
 test_all.js
 test_final.js
 test_interactive.js
+
+# Loop lock/log state
+.loop-locks/
+.loop-logs/

scripts/loop-guard.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+LANG=${1:?usage: loop-guard.sh <lang>}
+ROOT=$(cd "$(dirname "$0")/.." && pwd)
+cd "$ROOT"
+mkdir -p .loop-locks .loop-logs
+LOCK=".loop-locks/$LANG.claim"
+LOG=".loop-logs/$LANG.ndjson"
+NOW=$(date +%s)
+ISO=$(date -Iseconds)
+STALE_SEC=${LOOP_STALE_SEC:-1800}
+
+if [ -f "$LOCK" ]; then
+  LAST=$(cat "$LOCK" 2>/dev/null || echo 0)
+  AGE=$((NOW - LAST))
+  if [ "$AGE" -lt "$STALE_SEC" ]; then
+    printf '{"ts":"%s","lang":"%s","status":"skip","age":%d}\n' "$ISO" "$LANG" "$AGE" >> "$LOG"
+    echo "SKIP: $LANG claimed ${AGE}s ago (stale threshold ${STALE_SEC}s)"
+    exit 1
+  fi
+  echo "INFO: $LANG lock was ${AGE}s old, overtaking"
+fi
+
+echo "$NOW" > "$LOCK"
+printf '{"ts":"%s","lang":"%s","status":"claimed"}\n' "$ISO" "$LANG" >> "$LOG"
+echo "OK: $LANG claimed at $ISO"

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)"