V2 app: add new form component and polish form UI

[opencode-agent]

Summary

Form service and MCP elicitation are done.

The app needs to render the new V2 form component instead of the old prompt/form UI. A basic version may land soon, but proper styling, polish, and design need follow-up.

Related

• V2: add session form service #34973
• [FEATURE]: Port MCP lifecycle/status/connect/disconnect APIs to V2 #34435
• feat(core): add session form service #34855
• feat(core): MCP elicitation support  #35064
• TUI work is separate: feat(tui): render forms and route question tool through form service #35189

Source Discord URL: https://discord.com/channels/1391832426048651334/1520962938733723720/1522663895003697433

[opencode-agent]

Consolidated into #35067, which now owns app and TUI form UI implementation/polish. The requirement to replace the old app form surface with the new V2 form component has been carried over.