fix(skills): avoid skills watcher FD exhaustion

Watch SKILL.md only (and one-level SKILL.md in skill roots) to prevent chokidar from tracking huge unrelated trees.

Co-authored-by: household-bard <shakespeare@hessianinformatics.com>

src/agents/skills/refresh.test.ts

@@ -0,0 +1,64 @@
+import path from "node:path";
+import { describe, expect, it, vi } from "vitest";
+
+const watchMock = vi.fn(() => ({
+  on: vi.fn(),
+  close: vi.fn(async () => undefined),
+}));
+
+vi.mock("chokidar", () => {
+  return {
+    default: { watch: watchMock },
+  };
+});
+
+describe("ensureSkillsWatcher", () => {
+  it("ignores node_modules, dist, .git, and Python venvs by default", async () => {
+    const mod = await import("./refresh.js");
+    mod.ensureSkillsWatcher({ workspaceDir: "/tmp/workspace" });
+
+    expect(watchMock).toHaveBeenCalledTimes(1);
+    const targets = watchMock.mock.calls[0]?.[0] as string[];
+    const opts = watchMock.mock.calls[0]?.[1] as { ignored?: unknown };
+
+    expect(opts.ignored).toBe(mod.DEFAULT_SKILLS_WATCH_IGNORED);
+    expect(targets).toEqual(
+      expect.arrayContaining([
+        path.join("/tmp/workspace", "skills", "SKILL.md"),
+        path.join("/tmp/workspace", "skills", "*", "SKILL.md"),
+      ]),
+    );
+    expect(targets.every((target) => target.includes("SKILL.md"))).toBe(true);
+    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);
+  });
+});