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/tests/step59_test.cpp

@@ -217,7 +217,7 @@ int main() {
         WebSocketAgentServer server(std::move(transport));
 
         // Register a custom handler that knows about "getAST"
-        server.setRequestHandler([](const json& request) -> json {
+        server.setRequestHandler([](const json& request, const std::string&) -> json {
             std::string method = request.at("method").get<std::string>();
             json response;
             response["jsonrpc"] = "2.0";