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/network_plugin_test.cpp

@@ -205,15 +205,15 @@ int main()
         std::string long_key(1000, 'K');
         std::string json = "{\"" + long_key + "\":\"v\"}";
         auto h = parse_headers_json(json.c_str());
-        CHECK(h.size() == 1, "T4.3: 1000-char key, size=1");
-        CHECK(h[long_key] == "v", "T4.4: long key lookup works");
+        CHECK(h.empty(), "T4.3: 1000-char key rejected by MAX_HEADER_KEY_LENGTH");
+        CHECK(h.find(long_key) == h.end(), "T4.4: overlong key not inserted");
     }
     {
         std::string huge(10000, 'Z');
         std::string json = "{\"huge\":\"" + huge + "\"}";
         auto h = parse_headers_json(json.c_str());
-        CHECK(h.size() == 1, "T4.5: 10000-char value parsed");
-        CHECK(h["huge"].size() == 10000, "T4.6: size preserved");
+        CHECK(h.size() == 1, "T4.5: overlong value key parsed");
+        CHECK(h["huge"].size() == 8192, "T4.6: value truncated at MAX_HEADER_VALUE_LENGTH");
     }
     {
         auto h = parse_headers_json("{\"\":\"value\"}");