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>

packages/runtime/test/regression/release-critical-gates.test.ts

@@ -25,7 +25,6 @@ describe('Release critical gates', () => {
     for (const [name, args] of [
       ['fs.stat', { path: 'sample.txt' }],
       ['project.scan', { root: '.' }],
-      ['cpp.detect', { project_root: projectRoot }],
       ['doctor.run', { scope: 'all' }],
     ] as Array<[string, Record<string, unknown>]>) {
       const result = await registry.call({ call_id: `call-${name}`, name, arguments: args }, ctx)