feat(cli): emit OSC 9 notifications for responses

[monotykamary]

Summary

• emit OSC 9 notifications when assistant messages complete in TUI and opencode run
• share OSC 9 formatting/preview helper with tmux passthrough and safe truncation
• cache text parts to build notification previews and avoid JSON/piped output
• align OpenCode notifications with Codex/Claude Code behavior

Testing

[rekram1-node]

I think this makes sense, I forget if this is something opentui was gonna handle tho and then we'd implement the connection here

[monotykamary]

oh if it's on opentui's side, it might be a simpler hook on solid's side i believe