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/CodeEditorRenderHelpers.h

@@ -29,6 +29,10 @@
         return line;
     }
 
+    static bool isBracketChar(char c) {
+        return c == '(' || c == ')' || c == '[' || c == ']' || c == '{' || c == '}';
+    }
+
     static int lineFromMouseY(float mouseY, float baseY, float lineHeight, int lineCount) {
         int line = (int)((mouseY - baseY) / lineHeight);
         line = std::max(0, std::min(line, lineCount - 1));
@@ -311,4 +315,3 @@
             collectFoldNodes(ts_node_child(node, i), language, out);
         }
     }
-