Host driver tests

These fixtures are registered with CTest by the unit-test CMake project. The host-test pre-commit hook also runs them in CI when source or test files change. They can be built separately from the Ceedling suites:

cmake -S test/unit-test/host -B build/host-test -DCMAKE_BUILD_TYPE=Debug
cmake --build build/host-test --parallel 2
ctest --test-dir build/host-test --output-on-failure

Use GCC or Clang on Linux, or MinGW on Windows with its runtime DLLs on PATH. Set CMAKE_C_COMPILER when configuring to select a compiler explicitly.

• EHCI: actual driver code with simulated descriptor writeback and FRINDEX. Covers native FS, split transactions, HS, descriptor reuse, completion ordering/errors, cancellation, reset debounce and frame wrap. Shared QH/qTD pool tests cover mixed interrupt/ISO allocation, exhaustion, rollback and reuse. Builds ChipIdea with ISO disabled and enabled at queue depths 1, 2 and 4, and checks that the ISO flag keeps depth 1 on generic EHCI and MAX3421. Static DMA fixtures are linked below 4 GiB; hardware descriptor layouts are asserted separately from the native-pointer software tail.
• USBH/audio: actual stack and audio drivers with a stub HCD. Covers buffer ownership, queue capacity, callback dispatch, failed submissions, abort/close, capture/playback refill, underrun silence, feedback and reset timing. Builds generic, EHCI and MAX3421 configurations at depths 1, 2 and 4.

The 15 CTest cases retain assertions in release builds and have bounded execution times. They do not emulate DMA/cache coherency or USB wire timing; those still require hardware tests.