feat(acp): enable question tool for ACP clients

[Leoyzen]

Summary

Enable question tool support for ACP (Agent Client Protocol) clients like Zed. This allows ACP-compatible editors to handle AI assistant questions through their native permission UI.

Fixes #13752

What Changed

For ACP Users (Zed, etc.)

When the AI assistant asks a question (e.g., "Which test file should I create?"), ACP clients now display it as a native permission prompt with selectable options:

┌─────────────────────────────────────────┐
│  Create test file?                      │
│                                         │
│  ○ Unit tests (recommended)             │
│  ○ Integration tests                    │
│  ○ Skip this step                       │
│                                         │
│           [Cancel]                      │
└─────────────────────────────────────────┘

Implementation Details

1. Registry Update - QuestionTool is now available for ACP mode

   • Previously only available for app, cli, desktop clients
   • Now includes acp client type

2. Event Handler - New question.asked event handler in ACP Agent

   • Maps question options to ACP PermissionOption format
   • Generates unique option IDs from labels (kebab-case)
   • Always includes a "Cancel" option for dismissal
   • Uses existing permission queue for sequential per-session handling

3. Response Flow

   • User selects an option → calls sdk.question.reply() with the label
   • User clicks Cancel → calls sdk.question.reject()
   • Errors → gracefully rejected to prevent hanging promises

Scope & Limitations

This implements Phase 1 with the following constraints:

• ✅ Single-select only (first question if multiple)
• ✅ No text input (custom answers)
• ✅ Multiple options supported (array-based)
• ✅ Cancellation always available

Multi-select and text input support will come in a future update.

Testing

• 6 new integration tests in test/acp/question.test.ts
• All existing ACP tests pass (no regressions)
• bun test test/acp/ - 12 tests passing

Verification

# Run ACP tests
bun test packages/opencode/test/acp/question.test.ts

# Type check
bun run typecheck

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

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

Based on my search, I found a potential related PR:

Related PR:

• feat(acp): add opt-in flag for question tool #13562 - "feat(acp): add opt-in flag for question tool"
  • feat(acp): add opt-in flag for question tool #13562

This PR appears to be related to your current PR #13750 as it also addresses ACP question tool functionality. The PR #13562 involves adding an opt-in flag for the question tool, which may be complementary or overlapping with the feature being enabled in PR #13750.

You should verify if #13562 is:

1. A duplicate implementation of the same feature
2. A previous attempt that should be superseded
3. A related feature that should be coordinated

Otherwise, no duplicate PRs were found with the exact same scope.