batch3 T4 review polish: drop Stats hack, document cache race + total counting

- Drop unused Stats type import and its no-op suppression expression
- Comment getProjectFiles concurrent-miss race (benign, accepted)
- Comment findFiles deliberate post-limit counting (differs from grep)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/server/src/services/file_index.ts

@@ -15,6 +15,9 @@ interface CacheEntry {
 
 const cache = new Map<string, CacheEntry>(); // keyed by projectId
 
+// Concurrent calls with a cold/stale cache may both spawn rg. The result is
+// deterministic so they overwrite identically — no data corruption, just a
+// rare extra subprocess. Acceptable for single-user mode.
 export async function getProjectFiles(projectId: string, projectRoot: string): Promise<string[]> {
   const current = await snapMtimes(projectRoot);
   const cached = cache.get(projectId);