refactor: replace LocalOAIEngine with LocalAIEngine

[qnixsynapse]

Describe Your Changes

Migrate the legacy LocalOAIEngine abstraction to a new, generic LocalAIEngine base.

• Move all OpenAI type definitions to LocalAIEngineTypes and expose them via the engine index.
• Remove the old LocalOAIEngine files (and its test) and replace them with LocalAIEngine that defines the abstract API for local inference providers.
• Update the llamacpp-extension to extend LocalAIEngine instead of AIEngine.
• Adjust exports to include the new engine and types, and clean up unused imports.
• Add a new test suite for LocalAIEngine ensuring the abstract contract is satisfied.

Fixes Issues

• Closes #
• Closes #

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed
• Adjust FE code

[github-actions]

Barecheck - Code coverage report

Total: 30.03%

Your code coverage diff: -0.02% ▾

✅ All code changes are covered