2026-11-01

invalidation: Drop the derived ordering on Version

Summary:
Only the invalidation path merge compared versions, and it did so with the
derived lexicographic order, which happens to be right for two versions of
one chain: branch ids are minted in creation order and a branch is younger
than the one it was forked from. No behavior change here; the comparison is
the same, under a name that says when it is meaningful, and the guarantee it
rests on is written down on `BranchId`, which `CoreState::branches` already
relied on for its parents-before-children order.

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landed-with-radar-review

Differential Revision: D128864614

fbshipit-source-id: 95026364db3b164add47b5644d682a1cd6f24550