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/plugin-handlers/config-handler.ts

@@ -165,6 +165,7 @@ export function createConfigHandler(deps: ConfigHandlerDeps) {
       ...discoveredUserSkills,
     ];
 
+    const browserProvider = pluginConfig.browser_automation_engine?.provider ?? "playwright";
     const builtinAgents = await createBuiltinAgents(
       migratedDisabledAgents,
       pluginConfig.agents,
@@ -173,7 +174,8 @@ export function createConfigHandler(deps: ConfigHandlerDeps) {
       pluginConfig.categories,
       pluginConfig.git_master,
       allDiscoveredSkills,
-      ctx.client
+      ctx.client,
+      browserProvider
     );
 
     // Claude Code agents: Do NOT apply permission migration