Steps 266-268: Phase 10a — semantic annotation core + sidecar persistence (32/32 tests)

Step 266: 5 semantic annotation AST types (Intent, Complexity, Risk,
Contract, SemanticTag) with JSON roundtrip and compact AST integration.
Step 267: Sidecar AST persistence (.whetstone/<file>.ast.json) with
save/load/list RPC methods, MCP tools, and permission enforcement.
Step 268: Phase 10a integration tests — multi-file sidecar workflow,
all 5 types in compact view, idempotent roundtrip, source isolation.

Also includes Sprint 10 plan, GUI/installer polish, and Emacs integration fixes.

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

editor/src/ast/Annotation.h

@@ -141,3 +141,44 @@ class ConstExprAnnotation : public Annotation {
 public:
     ConstExprAnnotation() { conceptType = "ConstExprAnnotation"; }
 };
+
+// Semantic annotations for AI guidance (Sprint 10, Step 266)
+
+class IntentAnnotation : public Annotation {
+public:
+    std::string summary;   // 1-sentence description of what/why
+    std::string category;  // "validation", "transformation", "io",
+                           // "coordination", "computation", "initialization"
+    IntentAnnotation() { conceptType = "IntentAnnotation"; }
+};
+
+class ComplexityAnnotation : public Annotation {
+public:
+    std::string timeComplexity;    // "O(1)", "O(n)", "O(n^2)", etc.
+    int cognitiveComplexity = 0;   // 1-10 scale
+    int linesOfLogic = 0;
+    ComplexityAnnotation() { conceptType = "ComplexityAnnotation"; }
+};
+
+class RiskAnnotation : public Annotation {
+public:
+    std::string level;          // "low", "medium", "high", "critical"
+    std::string reason;
+    int dependentCount = 0;     // how many callers/consumers
+    RiskAnnotation() { conceptType = "RiskAnnotation"; }
+};
+
+class ContractAnnotation : public Annotation {
+public:
+    std::string preconditions;
+    std::string postconditions;
+    std::string returnShape;    // human-readable type/shape description
+    std::string sideEffects;    // "none", "io", "mutation", "network"
+    ContractAnnotation() { conceptType = "ContractAnnotation"; }
+};
+
+class SemanticTagAnnotation : public Annotation {
+public:
+    std::vector<std::string> tags;  // e.g. ["@serialize", "@validation"]
+    SemanticTagAnnotation() { conceptType = "SemanticTagAnnotation"; }
+};