test(facade): add QUIC facade tests and expand TCP facade coverage

[kcenon]

What

Summary

Add comprehensive unit tests for the QUIC facade (the only facade missing a dedicated test file) and significantly expand TCP facade test coverage with server creation, connection pool, SSL validation, interface conformance, and guard path tests.

Change Type

• Test

Affected Components

• tests/test_quic_facade.cpp - New QUIC facade test file (53 test cases)
• tests/test_tcp_facade.cpp - Expanded from 4 to 24+ test cases
• tests/CMakeLists.txt - Register QUIC facade test target

Why

Related Issues

• Relates to Add unit tests for facade and adapter layers #955 (Add facade/adapter unit tests)

Motivation

All five protocol facades (TCP, UDP, HTTP, WebSocket, QUIC) had existing tests except QUIC, which had no dedicated test file. TCP facade tests were sparse (only validation tests). This PR closes those coverage gaps by:

1. Creating test_quic_facade.cpp with full coverage of QUIC-specific features (ALPN, mutual TLS, 0-RTT, idle timeout, max connections)
2. Expanding TCP facade tests with server creation, connection pool, SSL validation, interface conformance, guard paths, and callback tests

How

Implementation Details

QUIC Facade Tests (test_quic_facade.cpp):

• Client config validation (empty host, port zero, zero idle timeout)
• Server config validation (port zero, empty cert/key paths, zero idle timeout, zero max connections)
• Client creation with various configurations (ALPN, CA cert, mutual TLS, custom timeout, 0-RTT)
• Server creation with various configurations (custom ID, ALPN, mutual TLS, custom max connections)
• Interface conformance (returned objects implement i_protocol_client/i_protocol_server)
• Guard paths (send on unconnected client, stop before start, connection count before start)
• Edge cases (port boundaries 1 and 65535, minimal idle timeout, minimal max connections)
• Callback setup (verify callbacks can be set before start without crashing)

TCP Facade Tests (expanded test_tcp_facade.cpp):

• Server creation (basic, custom ID, auto-generated ID, multiple servers)
• SSL not-implemented errors (server and client)
• Connection pool (creation, validation errors for empty host/port zero/pool size zero)
• Interface conformance (server returns i_protocol_server)
• Guard paths (connection count, stop before start, callback setup)
• SSL validation (missing cert, missing key, empty cert, empty key)
• Zero timeout validation

Test Plan

1. Tests follow existing project patterns (GTest fixtures, Result assertions)
2. No network connections required - tests validate configuration, creation, and guard paths
3. CI will verify compilation and test execution across all platforms

Checklist

• Tests follow project conventions
• No sensitive data exposed
• CMakeLists.txt updated with new test target
• Related issue linked

[github-actions]

Performance Comparison

Base Branch Results

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PR Branch Results

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[github-actions]

Coverage Report

Metric	Value
Line Coverage	62.4%
Target	75% (stretch: 80%)

Coverage Details

Full HTML report is available as a build artifact.