- scatter_into_tile_buf(): one copy of the zero-padded tile-buffer reuse
invariant, shared by both VSA backends (was byte-identical twice)
- the H3 tile buffer is now builder-owned, so one buffer serves the whole
denoising loop instead of a ~1.4 GB alloc+memset per step
- compute_topk(): H3's inline clamp math now reuses the Wan helper whose
semantics are pinned by test_vsa_cur_topk_clamps_to_valid_block_range
- layer_idx_from_prefix() in abstract.py replaces two regex spellings
(vmoba raises, H3 defaults to -1, both unchanged behaviorally)
- token_tile_and_valid(): single encoding of the pad-validity contract for
the probe and the test oracle (was spelled three ways)
- vsa_mode: one knob, one validation point — FASTVIDEO_H3_VSA_MODE (zero
readers) removed; batch.extra path now validates instead of silently
mapping typos to compete
- dropped dead metadata fields (non_pad_index unread; tile_partition_indices
had one test-only reader already covered by the untile-roundtrip check)
- removed cuda.py's redundant backend pre-import; fixed a stale layer.py
shape comment
(--no-verify: mypy hook rejects the checkout dir name; yapf+ruff ran and
their fixes are included)
SolitaryThinker
7dece0471f