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/agents/utils.test.ts

@@ -1,6 +1,7 @@
-import { describe, test, expect } from "bun:test"
+import { describe, test, expect, beforeEach } from "bun:test"
 import { createBuiltinAgents } from "./utils"
 import type { AgentConfig } from "@opencode-ai/sdk"
+import { clearSkillCache } from "../features/opencode-skill-loader/skill-content"
 
 const TEST_DEFAULT_MODEL = "anthropic/claude-opus-4-5"
 
@@ -109,6 +110,10 @@ describe("buildAgent with category and skills", () => {
   const { buildAgent } = require("./utils")
   const TEST_MODEL = "anthropic/claude-opus-4-5"
 
+  beforeEach(() => {
+    clearSkillCache()
+  })
+
   test("agent with category inherits category settings", () => {
     // #given - agent factory that sets category but no model
     const source = {
@@ -308,4 +313,42 @@ describe("buildAgent with category and skills", () => {
     // #then
     expect(agent.prompt).toBe("Base prompt")
   })
+
+  test("agent with agent-browser skill resolves when browserProvider is set", () => {
+    // #given
+    const source = {
+      "test-agent": () =>
+        ({
+          description: "Test agent",
+          skills: ["agent-browser"],
+          prompt: "Base prompt",
+        }) as AgentConfig,
+    }
+
+    // #when - browserProvider is "agent-browser"
+    const agent = buildAgent(source["test-agent"], TEST_MODEL, undefined, undefined, "agent-browser")
+
+    // #then - agent-browser skill content should be in prompt
+    expect(agent.prompt).toContain("agent-browser")
+    expect(agent.prompt).toContain("Base prompt")
+  })
+
+  test("agent with agent-browser skill NOT resolved when browserProvider not set", () => {
+    // #given
+    const source = {
+      "test-agent": () =>
+        ({
+          description: "Test agent",
+          skills: ["agent-browser"],
+          prompt: "Base prompt",
+        }) as AgentConfig,
+    }
+
+    // #when - no browserProvider (defaults to playwright)
+    const agent = buildAgent(source["test-agent"], TEST_MODEL)
+
+    // #then - agent-browser skill not found, only base prompt remains
+    expect(agent.prompt).toBe("Base prompt")
+    expect(agent.prompt).not.toContain("agent-browser open")
+  })
 })