feat: persist compact session state

shared/hooks/scripts/record-compact.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+set -euo pipefail
+root=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/../.." && pwd)
+mkdir -p "$root/.ai-session"
+printf '{"event":"compact","timestamp":"%s"}\n' "$(date -u +%Y-%m-%dT%H:%M:%SZ)" >> "$root/.ai-session/telemetry.jsonl"