feat: in-app browser for viewing local agent work

[khaliqgant]

Summary

Add an in-app browser panel so users can view locally-running web servers started by agents (e.g. npm run dev output on localhost) without leaving Pear.

Approach

Use an Electron <webview> tag (renderer-side, no main-process plumbing needed). Key behaviors:

• Auto-detect port from PTY output — parse localhost:\d+ / Local: http://... patterns from broker terminal stream and auto-navigate the webview
• URL bar with manual override for cases where the agent doesn't print a URL
• Nav controls — back, forward, reload
• Tab or side-panel layout (tab is simpler v1)

Implementation plan

• Enable webviewTag: true in BrowserWindow webPreferences
• LocalBrowser React component wrapping <webview> with URL bar + nav buttons
• Port-detection regex on PTY stream in broker.ts → IPC event to renderer
• Wire detected URL → webview loadURL
• Add browser tab/panel entry point in UI

Scope

localhost only — no external browsing needed. Estimated ~half a day for a solid v1.