computeMetadataDupRisk's self-row exclusion is case-sensitive while its own sibling check normalizes casing

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Context

computeMetadataDupRisk in packages/loopover-engine/src/opportunity-metadata.ts scans a peer-issue list to estimate duplicate risk, and its own self-row exclusion is inconsistent with the same-repo check two lines below it in the same loop body:

• Self-skip guard (opportunity-metadata.ts:184): peer.issueNumber === issue.issueNumber && peer.repoFullName === issue.repoFullName — exact, case-sensitive string comparison.
• Same-repo guard (opportunity-metadata.ts:186): peer.repoFullName.trim().toLowerCase() !== issue.repoFullName.trim().toLowerCase() — normalized.

This file already knows repo/login casing isn't guaranteed consistent across API responses — there's a dedicated test ("applies repo-specific goal specs case-insensitively") and sibling modules in this codebase (submission-freshness-check.ts, claim-conflict-resolver.ts) deliberately lowercase logins/repo names for the same documented reason. Line 184 is the one place in this function that didn't get the same treatment.

Requirements

• Normalize the self-skip comparison at opportunity-metadata.ts:184 to match the same casing/whitespace normalization already used at line 186 (.trim().toLowerCase()), so a peer entry that is the source issue itself — but with differently-cased repoFullName — is correctly excluded rather than counted as a duplicate of itself.
• No other logic in computeMetadataDupRisk changes — this is a one-line normalization fix, not a rewrite of the dup-risk algorithm.

Deliverables

• opportunity-metadata.ts:184's self-skip guard normalized the same way as line 186.
• A new test case in test/unit/opportunity-metadata-signals.test.ts (alongside the existing "computeMetadataDupRisk skips the source issue when scanning peers" test) covering a peer list containing the source issue with a differently-cased repoFullName, asserting dupRisk is unaffected (not inflated).

Test Coverage Requirements

This file is under src/ via the packages/loopover-engine workspace — confirm current coverage.include scoping for this package before assuming the top-level 99% patch gate applies exactly as src/** does; match whatever this package's existing test file already does for its coverage target. The new test must cover the normalized comparison.

Expected Outcome

computeMetadataDupRisk never counts the source issue as a duplicate of itself due to a casing mismatch in repoFullName between the source and its own echoed-back peer entry.

Links & Resources

• packages/loopover-engine/src/opportunity-metadata.ts:184 (the bug), :186 (the correct pattern to mirror)
• test/unit/opportunity-metadata-signals.test.ts (existing self-skip test to extend)

[linear-code]

JSO-5431