feat(skills): add agent-browser option for browser automation (#1090)

Add configurable browser automation allowing users to choose between
Playwright MCP (default) and Vercel's agent-browser CLI.

Changes:
- Add browser_automation_engine.provider config option
- Dynamic skill loading based on provider selection
- Comprehensive agent-browser CLI reference (inline in skills.ts)
- Propagate browserProvider to delegate_task and buildAgent
- Update documentation with provider comparison

Co-authored-by: Suyeol Jeon <devxoul@gmail.com>
Co-authored-by: YeonGyu Kim <code.yeongyu@gmail.com>

src/features/builtin-skills/skills.test.ts

@@ -0,0 +1,89 @@
+import { describe, test, expect } from "bun:test"
+import { createBuiltinSkills } from "./skills"
+
+describe("createBuiltinSkills", () => {
+	test("returns playwright skill by default", () => {
+		// #given - no options (default)
+
+		// #when
+		const skills = createBuiltinSkills()
+
+		// #then
+		const browserSkill = skills.find((s) => s.name === "playwright")
+		expect(browserSkill).toBeDefined()
+		expect(browserSkill!.description).toContain("browser")
+		expect(browserSkill!.mcpConfig).toHaveProperty("playwright")
+	})
+
+	test("returns playwright skill when browserProvider is 'playwright'", () => {
+		// #given
+		const options = { browserProvider: "playwright" as const }
+
+		// #when
+		const skills = createBuiltinSkills(options)
+
+		// #then
+		const playwrightSkill = skills.find((s) => s.name === "playwright")
+		const agentBrowserSkill = skills.find((s) => s.name === "agent-browser")
+		expect(playwrightSkill).toBeDefined()
+		expect(agentBrowserSkill).toBeUndefined()
+	})
+
+	test("returns agent-browser skill when browserProvider is 'agent-browser'", () => {
+		// #given
+		const options = { browserProvider: "agent-browser" as const }
+
+		// #when
+		const skills = createBuiltinSkills(options)
+
+		// #then
+		const agentBrowserSkill = skills.find((s) => s.name === "agent-browser")
+		const playwrightSkill = skills.find((s) => s.name === "playwright")
+		expect(agentBrowserSkill).toBeDefined()
+		expect(agentBrowserSkill!.description).toContain("browser")
+		expect(agentBrowserSkill!.allowedTools).toContain("Bash(agent-browser:*)")
+		expect(agentBrowserSkill!.template).toContain("agent-browser")
+		expect(playwrightSkill).toBeUndefined()
+	})
+
+	test("agent-browser skill template is inlined (not loaded from file)", () => {
+		// #given
+		const options = { browserProvider: "agent-browser" as const }
+
+		// #when
+		const skills = createBuiltinSkills(options)
+		const agentBrowserSkill = skills.find((s) => s.name === "agent-browser")
+
+		// #then - template should contain substantial content (inlined, not fallback)
+		expect(agentBrowserSkill!.template).toContain("## Quick start")
+		expect(agentBrowserSkill!.template).toContain("## Commands")
+		expect(agentBrowserSkill!.template).toContain("agent-browser open")
+		expect(agentBrowserSkill!.template).toContain("agent-browser snapshot")
+	})
+
+	test("always includes frontend-ui-ux and git-master skills", () => {
+		// #given - both provider options
+
+		// #when
+		const defaultSkills = createBuiltinSkills()
+		const agentBrowserSkills = createBuiltinSkills({ browserProvider: "agent-browser" })
+
+		// #then
+		for (const skills of [defaultSkills, agentBrowserSkills]) {
+			expect(skills.find((s) => s.name === "frontend-ui-ux")).toBeDefined()
+			expect(skills.find((s) => s.name === "git-master")).toBeDefined()
+		}
+	})
+
+	test("returns exactly 3 skills regardless of provider", () => {
+		// #given
+
+		// #when
+		const defaultSkills = createBuiltinSkills()
+		const agentBrowserSkills = createBuiltinSkills({ browserProvider: "agent-browser" })
+
+		// #then
+		expect(defaultSkills).toHaveLength(3)
+		expect(agentBrowserSkills).toHaveLength(3)
+	})
+})