test: add automated mesh protocol coverage

[Sayandevxyz]

Summary

Adds a comprehensive, hardware-free C++17 test suite (25 deterministic unit tests) covering all core protocol components of the Decentralized Mesh Protocol.

What Was Added

• ** ests/test_main.cpp** — Zero-dependency test harness with 25 unit tests
• CMakeLists.txt — New mesh_protocol_tests CMake target with enable_testing() / �dd_test() CTest integration
• .github/workflows/build.yml — CI now runs mesh_protocol_tests and ctest --output-on-failure automatically on every push/PR
• src/routing_engine.cpp — Implements missing RoutingEngine::clear_table() declared in header
• src/swarm_orchestrator.cpp — Implements missing SwarmOrchestrator::clear_tasks() declared in header

Why It Is Useful

The project had no automated regression tests. Any future change to packet serialization, routing logic, security, or task orchestration could silently break behavior with no detection. This PR ensures all core protocol contracts are verified on every commit.

Tests Covered

Component	Scenarios Tested
Packet Serialization	Roundtrip for all 6 PacketTypes; empty payload; max payload (64 bytes); oversized payload rejection; truncated buffer rejection; invalid magic byte rejection
CRC16 Integrity	Deterministic output; null/zero-length edge cases; single-bit corruption detection
Routing Engine	Self-beacon ignored; route insertion and lookup; RSSI/hop metric comparison; stale route pruning with 32-bit timer wraparound; clear_table()
Swarm Orchestrator	Priority ordering (highest first); task deduplication; incoming payload deserialization; orchestration cycle garbage collection; clear_tasks()
Security Engine	Key lifecycle (set/clear/invalid length); symmetric encrypt→decrypt roundtrip; nonce variation produces different ciphertext
Mesh Node	Sequence deduplication sliding window (100-entry); peer last-seen tracking; dead peer cleanup timeout

Validation

`�ash

Configure

cmake -B build -S . -DCMAKE_BUILD_TYPE=Release

Build both targets

cmake --build build

Run test suite directly

./build/mesh_protocol_tests

Or via CTest

ctest --test-dir build --output-on-failure
`

Result: 25/25 tests pass. Exit code 0.

Compatibility

• C++17 standard — no external testing framework required
• Desktop simulation (MinGW GCC, GCC/Clang on Linux/macOS, MSVC)
• Does not require ESP32/LoRa hardware, internet access, or proprietary software
• Existing mesh_node_sim target unchanged; tests compile against core source files only