[codex] Add managed browser pane

[OmGuptaIND]

Summary

• replaces the Playwright-based browser tool path with Anton-managed agent-browser sessions using Lightpanda for background browsing and isolated Chrome for the visible browser pane
• adds browser runtime status/install/repair flows through the Browser connector UI, including managed Lightpanda download and Chrome setup checks
• adds the inline browser pane with streaming frames, address bar, pointer/keyboard input, back/forward/reload/fullscreen controls, and polished panel sizing
• teaches the server to track the visible browser state so Anton can understand when the user is asking about the page currently open in the browser

Validation

• pnpm --filter @anton/protocol build
• pnpm --filter @anton/agent-core build
• pnpm --filter @anton/agent-server build
• pnpm --filter @anton/desktop typecheck
• pnpm --filter @anton/desktop build
• git diff --check
• make sync
• make verify reports the remote service running and ports 9876/9877 listening, but the public reachability check for port 9876 still fails from this workspace, matching the existing network-path issue.