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/GoGenerator.h

@@ -1,9 +1,12 @@
 #pragma once
 #include "ProjectionGenerator.h"
 #include "Import.h"
+#include "../SemannoAnnotationImpl.h"
 
-class GoGenerator : public ProjectionGenerator {
+class GoGenerator : public ProjectionGenerator, public SemannoAnnotationImpl<GoGenerator> {
 public:
+    std::string commentPrefix() const { return "// "; }
+
     std::string generate(const ASTNode* node) override {
         return dispatchGenerate(this, node, "// Unknown concept: ");
     }