fix(ai-sdk): make interpretation-intent override reliably win

PR #34's fixed +0.25 guidance gain was too small live: for "Was empfiehlt der
EDPB zum DSB?" the binding Art. 37 (1.381) still edged out the boosted EDPB
guidance (1.348), because the live authority score gives the binding article a
topic/domain bonus the (partly English) guidance chunk does not match.

Replace the fixed gain with a deterministic lift: a semantically competitive
guideline (raw semantic >= best_binding_semantic - 0.05) is lifted just ABOVE
the best binding FINAL score (ordered by semantic), so authority/topic/domain
bonuses can no longer edge it out. Obligation questions (no intent signal) are
untouched — binding stays Top-1; off-topic guidance stays demoted.

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

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

@@ -16,7 +16,7 @@ const (
 	scopePenalty         = 0.25 // BDSG Teil 3 (law enforcement) on a general DP question
 	topicGain            = 0.18 // amplifier only
 	supersededPenalty    = 0.50 // superseded Alt-Quelle (pre-eu-v1): demoted, nicht versteckt
-	guidanceIntentGain   = 0.25 // controlled guidance override on explicit interpretation intent
+	guidanceIntentGain   = 0.10 // epsilon a qualifying guideline is lifted ABOVE the best binding hit
 	guidanceIntentMargin = 0.05 // ...only if the guideline is semantically competitive with binding
 )
 
@@ -110,17 +110,36 @@ func rerankByAuthority(query string, results []LegalSearchResult) []LegalSearchR
 	copy(out, results)
 	for i := range out {
 		out[i].Score = authorityScore(query, out[i], qDomain, qForeign)
-		// Interpretations-Intent (eng begrenzt): NUR wenn die Query explizit nach
-		// Guidance/Auslegung fragt UND die Leitlinie semantisch konkurrenzfaehig ist
-		// (>= bester binding-Treffer - margin), darf supervisory_guidance die bindende
-		// Norm ueberholen. Sonst bleibt binding > guidance (Normfrage unveraendert).
-		if wantsGuidance && out[i].SourceClass == "supervisory_guidance" &&
-			results[i].Score >= bestBindingSem-guidanceIntentMargin {
-			out[i].Score += guidanceIntentGain
-		}
+	}
+	if wantsGuidance {
+		applyGuidanceIntent(out, results, bestBindingSem)
 	}
 	sort.SliceStable(out, func(a, b int) bool {
 		return out[a].Score > out[b].Score
 	})
 	return out
 }
+
+// applyGuidanceIntent lifts semantically-competitive guidance just ABOVE the best
+// binding hit (ordered by semantic), so an EXPLICIT interpretation question can
+// return guidance Top-1. Obligation questions (no intent → not called) keep
+// binding on top. Guidance below the semantic margin is left untouched, so an
+// off-topic guideline can never ride the override — and the lift is computed from
+// the binding FINAL score, so authority/topic/domain bonuses cannot edge it out.
+func applyGuidanceIntent(out, raw []LegalSearchResult, bestBindingSem float64) {
+	bestBindingFinal := 0.0
+	for i := range out {
+		if out[i].SourceClass == "binding_law" && out[i].Score > bestBindingFinal {
+			bestBindingFinal = out[i].Score
+		}
+	}
+	for i := range out {
+		if out[i].SourceClass != "supervisory_guidance" || raw[i].Score < bestBindingSem-guidanceIntentMargin {
+			continue
+		}
+		lifted := bestBindingFinal + guidanceIntentGain + (raw[i].Score - bestBindingSem)
+		if lifted > out[i].Score {
+			out[i].Score = lifted
+		}
+	}
+}