- Move isHtmlEntity to runtime.zig (was duplicated in codegen.zig and template.zig)
- Move appendTextEscaped to runtime.zig (was in template.zig)
- Add isXhtmlDoctype helper to runtime.zig for doctype detection
- Update template.zig to use codegen.void_elements instead of local isSelfClosing
- Update codegen.zig and zig_codegen.zig to use shared functions
- Update CLAUDE.md with shared utilities documentation
This establishes runtime.zig as the single source of truth for shared
utilities across all three rendering modes (codegen, template, zig_codegen).
- parser.zig: collect and merge all class values (shorthand and parenthesized) into single attribute
- Filter out empty, null, undefined class values during parsing
- Reverted redundant merging logic from codegen.zig, template.zig, zig_codegen.zig
- Added documentation about shared AST consumers relationship
- codegen.zig: collect class values and output as single merged attribute
- template.zig: respect quoted flag to prevent data lookup for static class values
- Added tests for multiple class merging scenarios
