test(adapters): add unit tests for 4 unified adapter modules

[kcenon]

Closes #967

Summary

• Adds unit tests for 4 unified adapter modules: ws_connection, ws_listener, quic_connection, quic_listener (68 new tests)
• Registers new targets in tests/CMakeLists.txt
• Updates CHANGELOG.md and docs/CHANGELOG.md

Why

Part of epic #953 — expand unit test coverage from 40% to 80%. The original issue #967 listed 17 adapter modules as untested, but gap analysis found 13 were already covered by #955. This PR completes the remaining 4.

Where

• tests/unit/test_ws_connection_adapter.cpp (+)
• tests/unit/test_ws_listener_adapter.cpp (+)
• tests/unit/test_quic_connection_adapter.cpp (+)
• tests/unit/test_quic_listener_adapter.cpp (+)
• tests/CMakeLists.txt (modified — 4 new test targets)
• CHANGELOG.md, docs/CHANGELOG.md (modified — Added entries)

How / Test plan

Local verification (macOS, bash 5.3, cmake 4.3):
cmake --preset release && cmake --build build
cd build && ctest --output-on-failure -L unit

Result: 196/196 adapter tests pass (0.66s), no GTEST_SKIP markers.

CI-required coverage:

• Ubuntu GCC/Clang, Windows MSVC, macOS
• Sanitizer variants (ASAN/TSAN/UBSAN)

Review Summary

• Gap analysis (Task 6): No critical findings — all 4 missing modules implemented, covers construction/error-paths per acceptance criteria.
• Code review (Task 7): Approved — no change requests (see team message log).
• No Minor/Info items outstanding.

Commits

• ae862a1 test(adapters): add unit tests for unified ws/quic adapters
• 36dfd6c docs(changelog): note adapter unit test additions for Add unit tests for adapter layer modules #967