chore(core): enable strict null checks

[bentatum]

Relates to

Type safety

Risks

Low

Background

What does this PR do?

Added type safety to evaluators in packages/core/src/runtime.ts to prevent crashes when parseJsonArrayFromText returns null. The fix uses evaluators?.includes to handle potential null values. Since strictNullChecks is disabled, similar issues likely exist elsewhere. I enabled strictNullChecks in the core package and kept changes minimal, focusing on the core runtime. Downstream TypeScript errors were addressed with ts-expect-error pragmas. This approach facilitates the incremental adoption of stricter type safety.

What kind of change is this?

Typescript related

Why are we doing this? Any context or related work?

The app crashes occasionally when parseJsonArrayFromText returns null in core runtime logic.

Documentation changes needed?

No

Testing

Integration tests should catch any issues. The only real change here is a null key check on evaluators in the evaluator handler loop.

Where should a reviewer start?

Start the app, make some prompts, make sure normal prompts work as expected.

Detailed testing steps