fix(tui): keep custom answer input focused while typing

[ziuus]

Issue for this PR

Closes #30393
Closes #41514

Type of change

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

What does this PR do?

Selecting "Type your own answer" in a question prompt opens the custom text input, but the input can't be typed into / submitted. Per #30393, the focused @opentui/core <textarea> swallows the Enter key, so the return -> submit binding never fires and typing is unreliable. Root causes and fixes:

1. TUI (packages/tui/src/routes/session/question.tsx): the editing-mode useBindings had no target, so the keymap didn't route keys to the <textarea> and the focused textarea captured Enter. Added target: textareaTarget and priority: 1, matching the DialogPrompt pattern which submits a focused textarea through the keymap.
2. CLI direct mode (packages/opencode/src/cli/cmd/run/footer.question.tsx): a createEffect re-ran on every keystroke (each onContentChange updates state), re-setting the textarea text and calling area.focus() on every character, fighting the user's input. Now it only syncs/focuses on the editing-mode transition.
3. App (packages/app/src/pages/session/composer/session-question-dock.tsx): added the 1–9 digit shortcuts to nav() for parity with the TUI, and as a direct way to reach the custom option.

How did you verify your code works?

• bun typecheck passes clean in packages/tui, packages/opencode, and packages/app.
• Question unit tests pass (bun test test/cli/run/question.shared.test.ts test/tool/question.test.ts -> 7 pass, 0 fail).
• Changes only reuse already-imported types and existing helpers.

Checklist

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

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Duplicate Found

PR #41079: feat(tui): type into custom form answers

• feat(tui): type into custom form answers #41079

This PR appears to address the same root issue: enabling typing into custom answer inputs in TUI question prompts. Your PR (#41517) is a fix that resolves the specific problem where the input wasn't receiving focus/keystrokes, while #41079 was a feature addition for the same functionality. They may have overlapping scope or one may have been superseded by the other.

[ziuus]

Regarding the duplicate flag: PR #41079 targets the form UI (packages/tui/src/routes/session/form.tsx, packages/tui/src/mini/footer.form.tsx). This PR targets the question prompt UI (packages/tui/src/routes/session/question.tsx, packages/opencode/src/cli/cmd/run/footer.question.tsx). They are separate components with separate input paths, so this is complementary rather than a duplicate.

[ziuus]

Updated the PR description: now Closes #30393 (the canonical issue for this bug) and Closes #41514 (which I opened and have closed as a duplicate). Note that #41079 targets the form UI while this PR targets the question prompt UI — different components.