pixtreme 1.7.0

pixtreme 1.7.0 adds two public capabilities. The first is the px.io.from_p210 / px.io.to_p210 pair, the tenth
named-format pair, which exchanges 10-bit 4:2:2 semi-planar frames (a uint16 Y plane followed by a uint16
interleaved Cb Cr plane, with the code in the upper 10 bits of each word) as one C-contiguous device array under the
existing 4:2:2 rules; the io module grows to 31 operations and the public API to 102. The second is the DCI
reference-white token for the SMPTE RP 431-2 D-Cinema white, accepted by px.color.chromatic_adaptation and
px.color.white_point_simulation. Both are additions: existing operations, signatures, defaults, and token spellings
are unchanged, and there are no breaking changes to the public API. The EXR reader and writer are reorganized
internally by compression, and corrupt-chunk errors now name the compression that failed. The published performance
baseline (docs/performance.md and the README table) is carried over from 1.6.0 unchanged and does not yet cover the
P210 pair.

Added

• Added the DCI reference-white token for the SMPTE RP 431-2 D-Cinema white (0.3140, 0.3510).
  px.color.chromatic_adaptation and px.color.white_point_simulation now accept it in either white argument.
  This adds no operation; the public API remains at 102 operations.
• Added px.io.from_p210 and px.io.to_p210, the tenth named-format pair. P210 is 10-bit 4:2:2 semi-planar
  (a uint16 Y plane followed by a uint16 interleaved Cb Cr plane) exchanged as a C-contiguous 1D device array.
  Each word carries a fixed 10 effective code bits in its upper 10 bits with no bit_depth argument; import ignores
  the lower six padding bits and export writes them as zero. range uses the H.273 mapping for n = 10, export
  rounds half away from zero and clips only to the code range [0, 1023], and the even-width constraint,
  horizontally co-sited chroma at full vertical resolution, and the interpolation tokens follow the existing 4:2:2
  rules. The io module now exposes 31 operations and the public API 102.

Changed

• EXR corrupt-chunk errors for RLE, PXR24, B44, B44A, and PIZ now name the compression whose chunk failed. The
  exception types and the situations that raise them are unchanged.