feat: add Vitest test infrastructure for agent and script validation (#337)

Adds Vitest + TypeScript test infrastructure for agent validation. Validates 642 agent files across 14 categories for YAML frontmatter, kebab-case naming, and directory population.

tests/install-validation.test.ts

@@ -0,0 +1,50 @@
+import { describe, it, expect } from "vitest";
+import { execSync } from "node:child_process";
+import * as fs from "node:fs";
+import * as path from "node:path";
+
+const ROOT = path.resolve(__dirname, "..");
+const SCRIPTS_DIR = path.join(ROOT, "scripts");
+
+describe("Install validation", () => {
+  describe("scripts/install.sh", () => {
+    const installSh = path.join(SCRIPTS_DIR, "install.sh");
+
+    it("should exist", () => {
+      expect(fs.existsSync(installSh)).toBe(true);
+    });
+
+    it("should pass bash syntax check (bash -n)", () => {
+      const result = execSync(`bash -n "${installSh}" 2>&1`, {
+        encoding: "utf-8",
+        timeout: 10_000,
+      });
+      // bash -n produces no output on success
+      expect(result.trim()).toBe("");
+    });
+  });
+
+  describe("scripts/install.ps1", () => {
+    const installPs1 = path.join(SCRIPTS_DIR, "install.ps1");
+
+    it.todo(
+      "should exist (PowerShell install script not yet available)"
+    );
+  });
+
+  describe("scripts/convert.sh", () => {
+    const convertSh = path.join(SCRIPTS_DIR, "convert.sh");
+
+    it("should exist", () => {
+      expect(fs.existsSync(convertSh)).toBe(true);
+    });
+
+    it("should pass bash syntax check (bash -n)", () => {
+      const result = execSync(`bash -n "${convertSh}" 2>&1`, {
+        encoding: "utf-8",
+        timeout: 10_000,
+      });
+      expect(result.trim()).toBe("");
+    });
+  });
+});