Steps 290-294: Phase 11a — Semanno format, annotation codegen, visitor dispatch (60/60 tests)

Semanno comment format standard (@semanno:type(key=value)) with emitter/parser
covering all 67+ annotation types. SemannoAnnotationImpl CRTP mixin provides
default visitor implementations for all 56 extended annotation methods across
7 language generators. Virtual inheritance resolves diamond ambiguity between
ProjectionGenerator and SemannoAnnotationImpl.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

editor/src/ast/JavaScriptGenerator.h

@@ -1,11 +1,14 @@
 #pragma once
 #include "ProjectionGenerator.h"
 #include "Import.h"
+#include "../SemannoAnnotationImpl.h"
 #include <unordered_map>
 #include <unordered_set>
 
-class JavaScriptGenerator : public ProjectionGenerator {
+class JavaScriptGenerator : public ProjectionGenerator, public SemannoAnnotationImpl<JavaScriptGenerator> {
 public:
+    std::string commentPrefix() const { return "// "; }
+
     explicit JavaScriptGenerator(bool includeTypes = false)
         : includeTypes_(includeTypes) {}