feat(ai-sdk): demote superseded pre-eu-v1 sources in authority rerank

The old pre-eu-v1 corpus chunks (un-annotated CRA/AI Act/DORA/NIS2/DSGVO
duplicates + the old Machinery Directive and its guide) are tagged
status=superseded / use_for_primary=false in the vector store. Honor that
in the rerank: a superseded result takes a fixed penalty so the eu-v1 norm
wins default questions, while the old source stays in the pool (demoted,
not hidden) and remains findable for history / transition questions.

Verified on dev: "CRA Sicherheitsupdates" now returns CRA Anhang I (eu-v1)
at #1 instead of an un-annotated old chunk; MaschinenVO outranks the old
Machinery Directive/guide; superseded chunks remain retrievable lower down.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ai-compliance-sdk/internal/ucca/legal_rag_client.go

@@ -148,6 +148,7 @@ func (c *LegalRAGClient) searchInternal(ctx context.Context, collection string,
 			CitationUnit:    getString(hit.Payload, "citation_unit"),
 			ReferencesOut:   getStringSlice(hit.Payload, "references_out"),
 			ReferencesIn:    getStringSlice(hit.Payload, "references_in"),
+			Superseded:      getString(hit.Payload, "status") == "superseded",
 		}
 	}