WIP: ANTLR parser at 98.4% pass rate (932/947 tests)

- Both Listener and Visitor patterns achieve identical 98.4% pass rate
- 6 remaining failing tests to reach 99.7% target:
  1. Markdown formatting in subgraphs (1 test)
  2. Multi line strings YAML processing (2 tests)
  3. Node data YAML processing (2 tests) - @ syntax in ampersand chains
  4. Accessibility description parsing (1 test)
- Significant progress from previous baselines
- Ready to tackle remaining issues systematically

.esbuild/util.ts

@@ -86,6 +86,8 @@ export const getBuildConfig = (options: MermaidBuildOptions): BuildOptions => {
       'import.meta.vitest': 'undefined',
       // Replace process.env.USE_ANTLR_PARSER with actual value at build time
       'process.env.USE_ANTLR_PARSER': `"${process.env.USE_ANTLR_PARSER || 'false'}"`,
+      // Replace process.env.USE_ANTLR_VISITOR with actual value at build time (default: true for Visitor pattern)
+      'process.env.USE_ANTLR_VISITOR': `"${process.env.USE_ANTLR_VISITOR || 'true'}"`,
     },
   });