When a claim is updated, deprecated, or superseded, a new assertion is
appended (append-only). Without dedup, fetch_authored_claims() returned
all versions, causing stale active copies to appear alongside the latest.
Now uses a HashMap keyed by claim ID, keeping only the version with the
highest assertion timestamp. All callers (scanner, CLI, ClaimStore,
export) get correct results automatically.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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