test(signals): full-branch coverage for duplicate-winner isDuplicateClusterWinnerByClaim

[JSONbored]

src/signals/duplicate-winner.ts is a pure, IO-free adjudicator with subtle tie/sparse-row branches. The existing 161-line test may not hit every arm of isDuplicateClusterWinnerByClaim (null claim on self, null claim on a sibling, equal-claim tie broken by PR number). Fill to 97%+ branch-counted coverage.

Deliverables

• Extend test/unit/duplicate-winner.test.ts (do not duplicate)
• isDuplicateClusterWinnerByClaim: empty siblings → true; self claim null → false; any sibling claim null → false; sibling claim earlier → false; equal claim + lower sibling number → false; equal claim + higher sibling number → true
• claimTimeMs: valid ISO, null/undefined, and unparseable string (NaN) branches via the public function
• Also confirm legacy isDuplicateClusterWinner min-based branch (sibling < prNumber vs not) is covered
• Verify each arm is hit with unsharded npm run test:coverage; test-only

References

• src/signals/duplicate-winner.ts:47
• src/signals/duplicate-winner.ts:38
• src/signals/duplicate-winner.ts:59
• test/unit/duplicate-winner.test.ts

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size: XS · gittensor:bug

[linear-code]

JSO-2225