chore: import upstream snapshot with attribution

src/lib/cliTools/batchStatusCache.ts

@@ -0,0 +1,47 @@
+// DRY: shared between /api/cli-tools/status and /api/cli-tools/all-statuses (plan 14 F2)
+// In-memory mtime-based cache for batch CLI tool status results.
+// Cache invalidated when mtime changes. Lives until server restart (no TTL).
+
+import type { ToolBatchStatus } from "@/shared/types/cliBatchStatus";
+
+export interface CacheEntry {
+  mtimeMs: number;
+  result: ToolBatchStatus;
+}
+
+/** Singleton in-memory cache: toolId → { mtimeMs, result } */
+const _cache = new Map<string, CacheEntry>();
+
+/**
+ * Get cached result for a toolId if mtime matches.
+ * Returns null if:
+ *  - entry doesn't exist
+ *  - stored mtimeMs !== provided mtimeMs (config file changed)
+ */
+export function getCached(toolId: string, mtimeMs: number): ToolBatchStatus | null {
+  const entry = _cache.get(toolId);
+  if (!entry) return null;
+  if (entry.mtimeMs !== mtimeMs) return null;
+  return entry.result;
+}
+
+/**
+ * Store a result in the cache for a toolId with its mtime.
+ */
+export function setCached(toolId: string, mtimeMs: number, result: ToolBatchStatus): void {
+  _cache.set(toolId, { mtimeMs, result });
+}
+
+/**
+ * Remove a specific toolId from the cache (e.g. after config write).
+ */
+export function invalidate(toolId: string): void {
+  _cache.delete(toolId);
+}
+
+/**
+ * Clear all cached entries. Primarily for testing isolation.
+ */
+export function clearCache(): void {
+  _cache.clear();
+}