Nine bit-width matrices in `turboquant::quantization` omitted
`TQBits::Bits1_5`, so the variant went unexercised there. This is the gap
#10390 closed for `quantize_output_byte_length`, where a `quantized_size`
double-padding bug had slipped through a hardcoded [Bits1, Bits2, Bits4]
list.
Add `Bits1_5` to the seven matrices that accept it, including the rstest
cases of `score_precomputed_dispatches_all_bit_widths`, whose name already
claims to cover every bit width.
The two `Unpadded` rotation tests keep their lists: `TurboQuantizer::new`
asserts "Bits1_5 requires TQRotation::Padded", since `Bits1_5` rotates
into its x1.5 padding and an unpadded rotation would leave half the codes
carrying nothing. Each list now names that invariant, so the omission
reads as deliberate rather than as the same oversight.
`unpadded_rotation_matches_padded_for_padding_free_dims` also claimed
multiples of 8 are padding-free "for every supported bit width", which
`Bits1_5` falsified: `padded_dim(8)` is 16.
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
