fix: keep @ file mention responsive on very large projects (#600)

Typing @ in the chat input to reference a file froze the app on huge
workspaces. Two compounding causes:

1. The autocomplete hook fed fileFilterQuery straight into the React
   Query key, so every keystroke fired a new directory_suggestions
   request and a fresh BFS scan on the daemon. Added a 180 ms debounce
   that mirrors the existing pattern in new-workspace-screen so rapid
   typing coalesces into one request.

2. searchWorkspaceEntries only ignored node_modules, so dist, build,
   target, out, coverage, vendor and __pycache__ each consumed the
   5,000-entry scan budget before any real source file was reached.
   Extended WORKSPACE_IGNORED_DIRECTORY_NAMES with those names and
   added a regression test that proves a deep source file is still
   reachable when those directories are full of bait entries.

Refs #599

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

packages/server/src/utils/directory-suggestions.test.ts

@@ -265,4 +265,34 @@ describe("searchWorkspaceEntries", () => {
     });
     expect(results.some((entry) => entry.path.startsWith("node_modules/"))).toBe(false);
   });
+
+  it("ignores common build/cache directories so large generated trees do not exhaust scan budget", async () => {
+    mkdirSync(path.join(workspaceDir, "packages", "app", "src"), { recursive: true });
+    writeFileSync(path.join(workspaceDir, "packages", "app", "src", "needle.ts"), "");
+
+    const heavyDirs = ["dist", "build", "target", "out", "coverage", "vendor", "__pycache__"];
+    for (const heavyDir of heavyDirs) {
+      for (let index = 0; index < 30; index += 1) {
+        mkdirSync(path.join(workspaceDir, heavyDir, `bundle-${index}`), { recursive: true });
+        writeFileSync(path.join(workspaceDir, heavyDir, `bundle-${index}`, "needle.ts"), "");
+      }
+    }
+
+    const results = await searchWorkspaceEntries({
+      cwd: workspaceDir,
+      query: "needle.ts",
+      limit: 20,
+      includeFiles: true,
+      includeDirectories: true,
+      maxEntriesScanned: 80,
+    });
+
+    expect(results).toContainEqual({
+      path: "packages/app/src/needle.ts",
+      kind: "file",
+    });
+    for (const heavyDir of heavyDirs) {
+      expect(results.some((entry) => entry.path.startsWith(`${heavyDir}/`))).toBe(false);
+    }
+  });
 });

packages/server/src/utils/directory-suggestions.ts

@@ -73,7 +73,16 @@ const directoryListCache = new Map<string, DirectoryListCacheEntry>();
 const workspaceEntryListCache = new Map<string, WorkspaceEntryListCacheEntry>();
 const NO_SEGMENT_INDEX = Number.MAX_SAFE_INTEGER;
 const NO_MATCH_OFFSET = Number.MAX_SAFE_INTEGER;
-const WORKSPACE_IGNORED_DIRECTORY_NAMES = new Set(["node_modules"]);
+const WORKSPACE_IGNORED_DIRECTORY_NAMES = new Set([
+  "node_modules",
+  "dist",
+  "build",
+  "target",
+  "out",
+  "coverage",
+  "vendor",
+  "__pycache__",
+]);
 
 export async function searchHomeDirectories(
   options: SearchHomeDirectoriesOptions,