fix(skills): ignore Python venvs and caches in skills watcher

Add .venv, venv, __pycache__, .mypy_cache, .pytest_cache, build, and
.cache to the default ignored patterns for the skills watcher.

This prevents file descriptor exhaustion when a skill contains a Python
virtual environment with tens of thousands of files, which was causing
EBADF spawn errors on macOS.

Fixes #1056

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/agents/skills/refresh.test.ts

@@ -12,7 +12,7 @@ vi.mock("chokidar", () => {
 });
 
 describe("ensureSkillsWatcher", () => {
-  it("ignores node_modules, dist, and .git by default", async () => {
+  it("ignores node_modules, dist, .git, and Python venvs by default", async () => {
     const mod = await import("./refresh.js");
     mod.ensureSkillsWatcher({ workspaceDir: "/tmp/workspace" });
 
@@ -21,11 +21,35 @@ describe("ensureSkillsWatcher", () => {
 
     expect(opts.ignored).toBe(mod.DEFAULT_SKILLS_WATCH_IGNORED);
     const ignored = mod.DEFAULT_SKILLS_WATCH_IGNORED;
+
+    // Node/JS paths
     expect(ignored.some((re) => re.test("/tmp/workspace/skills/node_modules/pkg/index.js"))).toBe(
       true,
     );
     expect(ignored.some((re) => re.test("/tmp/workspace/skills/dist/index.js"))).toBe(true);
     expect(ignored.some((re) => re.test("/tmp/workspace/skills/.git/config"))).toBe(true);
+
+    // Python virtual environments and caches
+    expect(ignored.some((re) => re.test("/tmp/workspace/skills/scripts/.venv/bin/python"))).toBe(
+      true,
+    );
+    expect(ignored.some((re) => re.test("/tmp/workspace/skills/venv/lib/python3.10/site.py"))).toBe(
+      true,
+    );
+    expect(ignored.some((re) => re.test("/tmp/workspace/skills/__pycache__/module.pyc"))).toBe(
+      true,
+    );
+    expect(ignored.some((re) => re.test("/tmp/workspace/skills/.mypy_cache/3.10/foo.json"))).toBe(
+      true,
+    );
+    expect(ignored.some((re) => re.test("/tmp/workspace/skills/.pytest_cache/v/cache"))).toBe(true);
+
+    // Build artifacts and caches
+    expect(ignored.some((re) => re.test("/tmp/workspace/skills/build/output.js"))).toBe(true);
+    expect(ignored.some((re) => re.test("/tmp/workspace/skills/.cache/data.json"))).toBe(true);
+
+    // Should NOT ignore normal skill files
     expect(ignored.some((re) => re.test("/tmp/.hidden/skills/index.md"))).toBe(false);
+    expect(ignored.some((re) => re.test("/tmp/workspace/skills/my-skill/SKILL.md"))).toBe(false);
   });
 });

src/agents/skills/refresh.ts

@@ -31,6 +31,15 @@ export const DEFAULT_SKILLS_WATCH_IGNORED: RegExp[] = [
   /(^|[\\/])\.git([\\/]|$)/,
   /(^|[\\/])node_modules([\\/]|$)/,
   /(^|[\\/])dist([\\/]|$)/,
+  // Python virtual environments and caches
+  /(^|[\\/])\.venv([\\/]|$)/,
+  /(^|[\\/])venv([\\/]|$)/,
+  /(^|[\\/])__pycache__([\\/]|$)/,
+  /(^|[\\/])\.mypy_cache([\\/]|$)/,
+  /(^|[\\/])\.pytest_cache([\\/]|$)/,
+  // Build artifacts and caches
+  /(^|[\\/])build([\\/]|$)/,
+  /(^|[\\/])\.cache([\\/]|$)/,
 ];
 
 function bumpVersion(current: number): number {