test: cover ECS component API

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Summary

• Adds a focused unit_ecs CTest binary for the new ECS C ABI.
• Covers lifecycle safety, component defaults, setter auto-add behavior, bounded tag handling, motion stepping filters, ECS_Each component filtering, and component name lookup.

Risky behavior now covered

• Shared ECS component state used by gameplay/scripting can regress in defaults, filters, or motion integration without requiring a full game-data runtime.

Test files added/updated

• Added tests/unit/test_ecs.cpp
• Updated CMakeLists.txt to register unit_ecs

Why this materially reduces regression risk

• The ECS module is a shared C++ core behind a C ABI. These tests verify the public ABI contracts most likely to affect gameplay logic and Lua bindings while remaining deterministic and independent.

Validation

• cmake --build build-test --target unit_ecs
• ctest --test-dir build-test -R '^unit_ecs$' --output-on-failure
• cmake --build build-test --target unit_macros unit_qmath unit_surfaceflags unit_qhelpers unit_crc unit_pathutil unit_msg unit_info unit_cm_bounds unit_parse unit_endian unit_vm_native_module unit_ecs && ctest --test-dir build-test -R '^unit_(macros|qmath|surfaceflags|qhelpers|crc|pathutil|msg|info|cm_bounds|parse|endian|vm_native_module|ecs)$' --output-on-failure