refactor(vscode): extract provider preference handlers

[marius-kilocode]

Summary

• Extract KiloProvider model preference persistence and enhance prompt handling into focused helpers.
• Keep existing message shapes and side effects while adding targeted unit coverage for favorites and enhance prompt paths.

Verification

• bun test tests/unit/model-preferences.test.ts tests/unit/enhance-prompt.test.ts
• bun run typecheck
• bun run lint

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (7 files)

• packages/kilo-vscode/src/KiloProvider.ts
• packages/kilo-vscode/src/kilo-provider/enhance-prompt.ts
• packages/kilo-vscode/src/kilo-provider/model-preferences.ts
• packages/kilo-vscode/src/provider-actions.ts
• packages/kilo-vscode/tests/unit/enhance-prompt.test.ts
• packages/kilo-vscode/tests/unit/model-preferences.test.ts
• packages/kilo-vscode/tests/unit/provider-actions-validate.test.ts

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_{Reviewed by gpt-5.5-20260423 · 179,825 tokens}