fix(vscode): improve question option contrast

[LEN5010]

Issue

Fixes #11794

Context

QuestionDock radio and checkbox outlines can blend into the background in low-contrast light themes such as Eva Light, making unselected options difficult to locate.

Implementation

Use VS Code's --vscode-button-background token for the default QuestionDock option-box border instead of the generic --border-base token.

This only changes the normal unselected border. Existing selected-state fill/border and focus-visible styles are unchanged.

Screenshots / Video

How to Test

Manual/local verification

• Built the VS Code Storybook successfully.
• Verified the QuestionDock story renders option controls with the updated theme token.
• Ran extension typecheck and lint successfully.
• Ran question-dock-contract.test.ts: 5 passed.

Reviewer test steps

1. Check out this PR.
2. Run bun install.
3. Run bun run extension from the repository root.
4. In the Extension Development Host, install and select the Eva Light color theme.
5. Open Kilo and trigger a question containing multiple-choice options.
6. Confirm each unselected radio/checkbox outline is clearly visible.
7. Select an option and confirm its existing selected state still renders normally.
8. Keyboard-focus an option and confirm its existing focus outline still appears.

Blocked checks and substitute verification

• The full VS Code unit suite completed 3024/3025 tests. The unrelated WorktreeManager.resolveStartPoint test expected remote but received local-tracking.
• Substitute verification: targeted QuestionDock tests, typecheck, lint, Storybook build, and pre-push cross-package typecheck passed.

Checklist

• Issue linked above, or exception explained
• Tests/verification described
• Screenshots/video included for visual changes, or marked N/A
• Changeset considered for user-facing changes
• I personally reviewed the diff and can explain the changes, including any AI-assisted work.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (2 files)

• packages/kilo-vscode/webview-ui/src/styles/question-dock.css
• .changeset/fix-question-option-contrast.md

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