Fix question keyboard focus and Enter submission

[bb-slop-cop]

🚨 SLOP COP 🚨 · new-issue-autopilot

Human comments

What was wrong

Numbered question shortcuts changed the selected answer without moving keyboard focus. The question form had no Enter handler for option answers, so pressing Enter afterward did not submit. Reproduction and root-cause report.

What changed

Focus the question container after a numbered option selection and route plain Enter on that container through the existing Next/Submit behavior. Child controls, free-text input, modifiers, composition, and disabled forms retain their existing behavior.

Two files changed: 88 additions + 3 deletions = 91 changed text lines. No dependencies, generated files, stored-data changes, or public contracts changed.

How you verified

• Authored the regression before changing production code; it failed in two clean checkouts of main at a13140a (expected one submission, received zero).
• pnpm exec turbo run test --filter=@bb/app -- src/components/thread/user-questions/QuestionForm.test.tsx: 13 tests pass after the fix, including multi-question and multi-select keyboard flows, modifier/composition guards, and free-text behavior.
• pnpm exec turbo run test --filter=bb-plugin-ask-user-question: 37 tests pass.
• pnpm exec turbo run typecheck --filter=@bb/shared-ui --filter=@bb/app and git diff --check pass.
• Chromium component harness: 2 then Enter fails on main and submits the second option with the fix. Full provider interaction and Brave/Omarchy were not tested; the reported click-option/Enter contrast was not reproduced on main.

Fixes #4137

AGENT GENERATED