Add comprehensive unit tests for code generator

Added extensive test coverage for the code generator including:

Test Cases:
- Simple component with string parameter
- Component with single channel parameter
- Component with multiple channels
- Component with mixed parameters (channels + regular)
- Component with complex HTML structure
- Component without parameters
- Multiple components in one file
- Complex widget with 5 parameters (2 channels, 3 regular)

Verification Coverage:
- Props struct generation
- Option function generation (With* functions)
- Component struct with channel fields
- Current value fields (current*) for channels
- BindApp method generation
- Channel listener goroutine methods
- Proper "for val := range" syntax
- Update() calls in listeners
- Multiple channel listeners per component
- Render method with runtime.* calls
- Interface method generation (Mount, Unmount, Update)
- Import generation
- Code generation comment header

These tests ensure channel-based reactive state management is correctly
generated for all component configurations.

Author: claude