feat(gateway): strategie rerank oltre la search (A-F)

- A: gate store con cross-encoder — guardrail.decide async, conferma/scarta
  quasi-duplicati (CROSS_DUP_CONFIRMED/WEAK/LOW_COSINE), suggerimento
  supersedes in WARN, degrada a cosine-only se il reranker è giù
- B: verifica supersede — cross-score (nuovo,vecchio) sotto soglia →
  supersede_warning non bloccante + audit
- C: score composito in search — rerank + importance (nuovo campo payload)
  + recency decay (180gg) + authority, pesi SCORE_W_* da env
- E: multi-query — SearchIn.queries (max 3), pool unito con dedup, rerank
  unico; endpoint POST /v1/score come primitiva cross-encoder (F-lite)
- extension search.ts: param queries + rerank_score/composite in output
- D: scripts/consolidate.py — dedup periodico a coppie via cross-encoder
  con report ntfy e --apply via gateway
- test: 69 pass (+11 strategie); guardrail_version similarity-v2

gateway/store.py

@@ -64,6 +64,7 @@ def format_results(hits: list[Any]) -> list[dict]:
             "scope": h.payload.get("scope"),
             "project_id": h.payload.get("project_id"),
             "confidence": h.payload.get("confidence"),
+            "importance": h.payload.get("importance", 0.5),
             "created_at": h.payload.get("created_at"),
             "source": h.payload.get("source"),
             "supersedes_id": h.payload.get("supersedes_id"),