A single-tier fixture cannot fail "GetTier ignores lot quality": every
lot resolves to the only tier regardless of its own Quality. Added a
second tier (Rare, threshold .5) and a second lot whose quality (.6)
lands in it, and asserted GetTier resolves each lot to its own tier.
Also asserts that minting a second instance from an existing lot does
not re-roll the lot's quality.
Verified by mutation, then reverted: GetTier hardcoded to a fixed
quality, and CreateInstance(int) re-rolling the lot's quality, both
fail this test. 36 of 36 tests pass on the real fix.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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