feat(checker): Add satisfies operator and type assertions checking

Implement type checking for TypeScript's satisfies operator and type assertions:

## Satisfies Operator (satisfies.rs)
- Check `expression satisfies Type` expressions
- Preserve narrower inferred type while validating against target type
- Support const assertion interaction with satisfies
- Proper handling of literal types preservation
- Validates assignability without widening

## Type Assertions (assertions.rs)
- Check `as T` syntax type assertions
- Check `<T>` angle bracket assertions (with TSX detection)
- Check `as const` assertions for literal preservation
- Implement non-null assertion operator (!)
- Validate assertion compatibility rules (type overlap)
- Handle assertion to/from unknown and any
- Support double assertion escape hatch pattern

## Key Features
- 35 new tests covering all assertion/satisfies scenarios
- Integration with TypeChecker for consistent options
- Proper error codes matching TypeScript diagnostics
- Support for strict null checks mode

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: mohsen1