fix(review): 对齐 round3-F 改动的测试和边界规则

- tool-stubs.test.ts: 旧 cpp.cmake.configure/static.cppcheck/clangd.query
  名字已删，改为验证 CppToolRegistrar 独立注册
- release-critical-gates.test.ts: cpp.detect 不再由 BuiltInToolRegistrar
  注册，从 built-in envelope 测试移除
- .dependency-cruiser.js: 允许 runtime → toolchain-cpp (capability
  registration boundary, INV-4 compliant)

e2e: 14/14 gates passed

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.dependency-cruiser.js

@@ -57,15 +57,15 @@ module.exports = {
       },
     },
 
-    /* ── Rule 4: runtime may only import from contracts & llm ── */
+    /* ── Rule 4: runtime may only import from contracts, llm & toolchain-cpp ── */
     {
       name: "runtime-boundary",
-      comment: "runtime may only depend on contracts and llm (facade)",
+      comment: "runtime may only depend on contracts, llm (facade), and toolchain-cpp (capability registration)",
       severity: "error",
       from: { path: "^packages/runtime/src/" },
       to:   {
-        path: "^packages/(tui|cli|workers|toolchain-cpp)/",
-        pathNot: "^packages/(contracts|llm)/",
+        path: "^packages/(tui|cli|workers)/",
+        pathNot: "^packages/(contracts|llm|toolchain-cpp)/",
       },
     },