test(fs): tighten cap assertion and add nested-path case per Greptile review

- Use toBe(50_000) for flat input — zero derived directories means total === cap
- Add test documenting that entries total can exceed 50k when nested paths
  produce extra directory entries via deriveDirectories (cap is on raw files,
  not on the final files+dirs result)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TpGjPYBD4pgZpsAHjozzsN

Author: 2 people

packages/workspace-server/src/services/fs/service.test.ts

@@ -58,14 +58,34 @@ describe("FsService.listRepoFiles", () => {
 
   it("caps file list at MAX_REPO_FILES when repo is very large", async () => {
     vi.mocked(getChangedFiles).mockResolvedValue(new Set());
+    // Flat paths produce zero derived directory entries, so total === cap.
     const bigList = Array.from({ length: 60_000 }, (_, i) => `file${i}.ts`);
     vi.mocked(listFiles).mockResolvedValue(bigList);
     vi.mocked(listUntrackedFiles).mockResolvedValue([]);
 
     const service = new FsService();
     const entries = await service.listRepoFiles("/repo");
 
-    expect(entries.length).toBeLessThanOrEqual(50_000);
+    expect(entries.length).toBe(50_000);
+  });
+
+  it("total entries can exceed MAX_REPO_FILES when derived directories are included", async () => {
+    vi.mocked(getChangedFiles).mockResolvedValue(new Set());
+    // Nested paths cause deriveDirectories to add parent directory entries on
+    // top of the capped 50k file entries, so the returned total is > 50k.
+    const bigList = Array.from(
+      { length: 60_000 },
+      (_, i) => `src/sub${i}/file.ts`,
+    );
+    vi.mocked(listFiles).mockResolvedValue(bigList);
+    vi.mocked(listUntrackedFiles).mockResolvedValue([]);
+
+    const service = new FsService();
+    const entries = await service.listRepoFiles("/repo");
+
+    const fileEntries = entries.filter((e) => e.kind === "file");
+    expect(fileEntries.length).toBe(50_000);
+    expect(entries.length).toBeGreaterThan(50_000);
   });
 
   it("omits untracked files when git ls-files --others is aborted", async () => {