Scorer reform-vector cache lane needs a real mode digest (advisory from #557 round 3)

From the #557 round-3 confirm, advisory severity — scorer-only, no release exposure. The explicit-None materializer declaration separates scorer vectors from release vectors, but within the scorer lane two collision routes remain: (1) --legacy-pe-flat-h5 changes frame loading but is absent from the retained cache keys, so a doubly-readable/hybrid H5 can share every retained key while producing different frames; (2) state-file vectors are positional while collection hashing sorts state names but concatenation uses tuple order. Fix shape: replace the bare None with a scorer/mode digest (loader mode + ordered collection identity) so the declaration is a complete identity rather than a lane tag. Cites: tools/score_us_fiscal_targets.py / tools/score_us_state_files.py cache-context blocks; PR #557 round-3 review.

Start by comparing the cache-context blocks in tools/score_us_fiscal_targets.py and tools/score_us_state_files.py, then trace how loader mode and collection ordering enter the retained keys. Done means the scorer declaration uses a mode digest covering the loader mode and ordered collection identity, preventing both described collision routes.