feat(enrichment): merge-conflict-marker / leftover-artifact analyzer

[JSONbored]

New REES local analyzer that flags leftover VCS conflict markers (<<<<<<<, =======, >>>>>>>) and rebase/patch artifacts accidentally committed in added lines — a mechanical but high-value catch that should block a merge. Pure compute, no network, near-zero false-positive.

Deliverables

• Add ConflictMarkerFinding ({ file, line, marker: string }) + conflictMarker? key to review-enrichment/src/types.ts
• Create review-enrichment/src/analyzers/conflict-marker.ts: match conflict-marker line shapes on added lines only; guard against legitimate ======= in markdown/asciidoc rules where cheap; cap with maxFindings
• Register a local descriptor (category 'quality', cost 'local', requires ['files']) with inline render() in review-enrichment/src/analyzers/registry.ts
• Add review-enrichment/test/conflict-marker.test.ts covering each marker flagged, a markdown horizontal rule not flagged, and the cap

References

• review-enrichment/src/analyzers/actions-pin.ts (added-line hunk walk template)
• review-enrichment/src/analyzers/registry.ts:158-175
• review-enrichment/src/types.ts:289-311

Part of #1499.

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size: XS · gittensor:bug

[linear-code]

JSO-2149