Centralize the IndexCache skip formula and thread the resulting active logical index layers into NSA KV pools. HiCache now skips only the indexer H2D/D2H payload for inactive target layers while preserving per-layer MLA KV transfer, keeping allocation shape unchanged for this phase.
Constraint: P0-P2 must not compact device or host allocation yet; prefill/decode state transfer still has no logical layer-id metadata.
Rejected: Recompute the skip formula separately in mem_cache | formula drift would corrupt cache or waste transfers when offset/pattern settings change.
Rejected: Skip whole-layer HiCache load/backup | MLA KV remains required for every attention layer.
Confidence: medium
Scope-risk: moderate
Directive: Before enabling compact state buffers or compact allocation, add layer-id metadata validation to PD transfer.
Tested: Local py_compile for touched files; remote pytest in g0034 container: test_nsa_index_layers.py and TestNSAIndexerPageIndices, 20 passed.
Not-tested: ETE replay/GSM8K with --nsa-index-topk-freq 4; PD state-transfer compaction remains unimplemented.
d21952b903