fix(opencode): prevent Warp Windows tab close on TUI exit

[NicoAvanzDev]

Issue for this PR

Closes #24790

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Warp on Windows closes the tab when the TUI exits from OpenTUI alternate-screen mode. This changes the TUI renderer to use main-screen mode only for Warp on Windows, while keeping the existing renderer behavior for other terminals. It also consumes the app-exit key before tearing down the prompt so Ctrl+D does not leak to the shell after exit.

How did you verify your code works?

• Ran bun typecheck from packages/opencode.
• Ran bun run script/build.ts --single --skip-install --skip-embed-web-ui from packages/opencode.
• Manually tested the built Windows binary in Warp with /exit and Ctrl+D.

Screenshots / recordings

Not included. This is terminal exit behavior; manual verification confirmed the Warp tab now stays open and returns to the shell.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Hey! Your PR title Fix Warp Windows TUI exit doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[NicoAvanzDev]

Closing in favor of the alternate Windows console teardown fix, which has been tested locally.