feat: show remote host and cwd in taskbar when using attach

[simondmorias]

Summary

• When using opencode attach <url>, the taskbar previously showed the local directory which was confusing.
• Now displays the remote host:port and the server's working directory
• Shows format: host:port /remote/path:branch (e.g., myserver.com:4096 /home/user/project:main)

Changes

• Add attached flag to distinguish attach mode from normal mode
• Parse and expose remoteHost from connection URL in SDK context
• Fetch remote directory via /path endpoint during bootstrap
• Update useDirectory() hook to show remote info when attached

Testing

• Manual run: bun run --cwd packages/opencode --conditions=browser src/index.ts attach http://localhost:4096