[js-api-parser] Refactor JS API view Parser - Phase 1

### Phase 1: Core Top-Level Items (P0)

**Goal**: Replace most common API patterns with semantic generators

1. **Class Generator** (`ApiItemKind.Class`)
- Access modifiers: `public`, `private`, `protected`
- Abstract classes
- Type parameters with constraints
- `extends` and `implements` clauses
- Handle members separately (they have their own generators)

2. **Interface Generator** (`ApiItemKind.Interface`)
- Type parameters with constraints
- `extends` clauses
- Handle members separately

3. **Method/MethodSignature Generators**
- Static vs instance
- Access modifiers
- Optional/rest parameters
- Overload handling (if needed)
- Async functions

**Testing**:
- Create test fixtures for each generator
- Unit tests with API model objects
- Integration tests comparing output with legacy approach

**Success Criteria**:
- All P0 generators implemented
- Test coverage > 90%
- Zero regressions on existing API JSON files