The spacing eviction in create_checkpoint() keeps the oldest checkpoint and
erases every later one within checkpoint_min_step of it. For prompts shorter
than checkpoint_min_step this drops the checkpoint at n_tokens - 4 that the
next request resumes from, so hybrid/recurrent models re-prefill from the
previous checkpoint instead. Apply the spacing rule only once the list is at
n_ctx_checkpoints, and replace an existing checkpoint at the same n_tokens
instead of appending a duplicate.
* metal : fix half-idle simdgroup in kernel_mul_mv_iq3_xxs_f32 for ne00 < 1024
* metal : keep N_R0_IQ3_XXS = 4, dispatch a separate 8-row split kernel for ne00/32 < 32
The plain kernel is unchanged from master (4 rows per simdgroup, one thread per
chunk). The row-split mapping now lives in a separate kernel_mul_mv_iq3_xxs_f32_split
instantiation with N_R0_IQ3_XXS_SPLIT = 8, and the host selects it only when
ne00/32 < 32 and divides 32, so wide matrices keep the master kernel bit for bit.
* metal : select the iq3_xxs row split with a function constant instead of a separate kernel
Foad Abo Dahood