Add shared instruction files and copilot history maintenance scripts

- Add 12 cross-project instruction files to resources/instructions/
- Add cleanup-copilot-history.mjs/.sh: quarantine-based history cleanup with dry-run and aggressive scope
- Add restore-copilot-history.mjs/.sh: restore from quarantine by run, path, or filter
- Add purge-copilot-history-quarantine.mjs/.sh: purge old quarantine runs with keep-latest guard
- Add copilot-history-maintenance.test.mjs: 3 passing unit tests covering all three scripts

resources/scripts/purge-copilot-history-quarantine.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+script_dir="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd -P)"
+
+if command -v node >/dev/null 2>&1; then
+  node_bin="$(command -v node)"
+elif command -v nodejs >/dev/null 2>&1; then
+  node_bin="$(command -v nodejs)"
+else
+  printf 'Node.js is required to purge Copilot history quarantine runs.\n' >&2
+  exit 1
+fi
+
+exec "$node_bin" "$script_dir/purge-copilot-history-quarantine.mjs" "$@"