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/lsp_plugin_test.cpp

@@ -5,6 +5,8 @@
 //   - lsp_trim: 字符串 trim 逻辑
 //   - lsp_frame_message: Content-Length header 构建
 //   - lsp_parse_content_length: Content-Length header 解析
+// 说明: 本测试仅覆盖纯函数路径；不覆盖 reader_loop 并发、进程生命周期或
+// Server->Client Request 集成路径，这些需由 smoke/集成测试覆盖。
 // ============================================================================
 
 #include "lsp_internal.hpp"