C-238 evidence: bound-range list concatenation materializes on every leg

[O6lvl4]

Greenfield fuzz catch #4 (2026-08-21, differential seeds 47/83/89, new range-bind generator arm): [1, 2] + r where r is a let-bound range.

• Native (0.58.0) and the greenfield wasm leg both answer the materialized list ([1, 2, 0, 1]).
• The greenfield reference evaluator's ConcatList arm accepted only (List, List) operands and aborted internal: list concat — fixed in greenfield 9e6049d65 (ConcatList now takes List|Range through as_iter_items; over-cap spans abstain like index/len, C-197 territory).
• The fixture pins the bound var AND the syntactic value-position forms (range as either concat operand, range inside a slice argument) so the materializing readings are covered from both spellings.
• Verified on native: 0␤1␤[1, 2, 0, 1]␤[3, 4, 5, 7]␤[1, 2]␤ exit 0. contracts.toml evidence row added under C-238; conformance.md and README regenerated; check-contracts.sh and check-als-style.sh green (593/593 fixtures linked).

Greenfield will claim the row at the next als pin bump (2-PR flow).

🤖 Generated with Claude Code