Add native HistoryCodec unit tests

[LorenzoLongaretto]

Description

Add 22 Unity tests covering encode/decode roundtrip, NaN sentinel preservation, anchor frame boundaries, varint, edge cases, and buffer overflow protection.

• New env [env:native_history] in platformio.ini
• New test/test_history_codec/test_main.cpp
• Compiles production HistoryCodec.cpp directly (no copies)
• All tests self-contained, no hardware dependencies
• Run: pio test -e native_history

Type of Change

• Bug fix
• New feature
• Documentation update
• Refactoring
• Other (describe):

Testing

Describe how you tested these changes:

• Compiled with pio run -e pico_w_release
• Ran unit tests (pio test -e native)
• Tested on hardware

Checklist

• Code follows project conventions
• Comments are in English
• No new compiler warnings introduced
• Flash usage remains under 100%

Related Issues

Closes #38

[angeloINTJ]

Merged — thanks @LorenzoLongaretto! Really solid work on the test suite. The anchor frame boundary tests and NaN compression coverage are exactly what this codec needed.

First community contribution to SIMUT 🎉 Hope you stick around — there are more subsystems waiting for tests if you're interested.

[LorenzoLongaretto]

Wow, thanks for the kind words! Genuinely glad the coverage landed well. I'll definitely stick around — already curious about those other subsystems. Just point me in the right direction whenever 😄