W23: close mailroom metadata and network validation tests

- Refresh agents STATUS to W22.6 and exclude mailroom from metadata scans
- Add mailroom dispatch checklist and defensive rules
- Register F-23.D-1 and tag network input validation defense-in-depth
- Update network plugin tests for header length limits
- Fix LSP test metadata and remove orphan anthropic_internal.hpp

Verification:
- cmake --build build --config Release: 0 error, 0 warning
- ctest --test-dir build --output-on-failure: 10/10 passed
- ctest --test-dir build -R dstalk_smoke_test --output-on-failure: passed
- python scripts/check_agents_metadata.py --strict: passed

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/CMakeLists.txt

@@ -213,7 +213,7 @@ target_link_libraries(dstalk_network_plugin_test
 add_test(NAME dstalk_network_plugin_test COMMAND dstalk_network_plugin_test)
 
 # ============================================================
-# dstalk_lsp_plugin_test — LSP 插件单元测试 (GoogleTest, 新增)
+# dstalk_lsp_plugin_test — LSP 插件单元测试 (hand-rolled CHECK, 新增)
 # 覆盖: lsp_trim / lsp_frame_message / lsp_parse_content_length
 # ============================================================