Decode packaged byte 0 as separate block-height and block-depth nibbles,
including explicit zero dimensions, and size linear compressed textures
by pixel rows. Port the driver-derived rules from PR #201 and preserve
its attribution to digitalhivehub's PR #11 measurements.
Integrate the layout test with current main, correct its BC4 label, add
independently addressed CPU markers and packaged GPU mip coverage, and
record the mechanisms in the reference docs and symptom index.
Validation: 9 driver shapes, 189 CPU texture checks (also ASan/UBSan),
17 GPU deswizzle cases, 154 NVN checks, documentation checks, Mac host
build, and iOS compilation of 133 sources pass. No new gameplay or
iPhone runtime validation.
Co-authored-by: Aleksandr Svidchenkov <a.svidchenkov@gmail.com>
