mavend: Nexus says which name it knows, we do not pick (V-524)

entityReferenceText returned the longest Latin run in the utterance, which is a
guess dressed as a rule. "перезапусти nginx на muzick-indexer" holds two names,
the target is not the longer one, and docs/ecosystem.md already says what to do
instead: ambiguous resolution asks the owner, it does not pick. Nexus owns which
names it knows.

So entityReferences returns every Latin run, in the order he said them, capped
at four so one utterance cannot fan out into a dozen HTTP calls.
resolveEntityCandidates asks about each and stops as soon as the answer is
decided: a Nexus failure ends it and reports degradation, Nexus calling one name
ambiguous ends it with its candidates, and two names resolving to different
entities is our own clarify listing the names Nexus spells. One resolving is the
target, none resolving falls through as before.

The transliteration signal is unchanged — the recovery still fires only when the
utterance carries a Latin run and the model's Text slot carries none.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XGTGCWX33aX8SMBSRz9VmS

cmd/mavend/ecosystem_acts.go

@@ -533,6 +533,64 @@ func traceErrorFields(err error) map[string]any {
 	return fields
 }
 
+// entityResolution — what asking Nexus about a turn's candidate names came to.
+// One shape rather than five return values, because the caller needs the
+// reference that answered as well as the answer: it goes in the trace.
+type entityResolution struct {
+	subject     string   // the reference Nexus answered about
+	entityID    string   // set when exactly one name resolved
+	displayName string   // that entity's name as Nexus spells it
+	ambiguous   []string // candidate display names to ask between
+	err         error    // a dependency failure, not a miss
+}
+
+// resolveEntityCandidates asks Nexus about each name the turn offered and
+// reports what it knows, stopping early where the answer is already decided.
+//
+// The rules, in the order they apply:
+//
+//   - A dependency failure ends it. Nexus being down is not "no such entity",
+//     and asking about the next name would report the outage as a miss.
+//   - Nexus calling one name ambiguous ends it. It has the candidates and it is
+//     telling us to ask.
+//   - Two names resolving to different entities is a clarify too, this time ours:
+//     "перезапусти nginx на muzick-indexer" names both a service and its host,
+//     and picking either would be inventing an intent he did not state.
+//   - Nothing resolving returns the first name as the subject, so the trace says
+//     what was actually looked for.
+func (h *reactiveHandler) resolveEntityCandidates(ctx context.Context, refs []string) entityResolution {
+	var out entityResolution
+	for _, ref := range refs {
+		entityID, displayName, ambiguous, err := h.ecosystem.resolveEntityReference(ctx, ref, nil)
+		if err != nil {
+			return entityResolution{subject: ref, err: err}
+		}
+		if len(ambiguous) > 0 {
+			return entityResolution{subject: ref, ambiguous: ambiguous}
+		}
+		if entityID == "" {
+			continue
+		}
+		if out.entityID == "" {
+			out = entityResolution{subject: ref, entityID: entityID, displayName: displayName}
+			continue
+		}
+		if entityID == out.entityID {
+			continue
+		}
+		// Both are real and they are not the same thing. Hand back the names
+		// Nexus spells, not the words he happened to say.
+		return entityResolution{
+			subject:   out.subject,
+			ambiguous: []string{out.displayName, displayName},
+		}
+	}
+	if out.entityID == "" && len(refs) > 0 {
+		out.subject = refs[0]
+	}
+	return out
+}
+
 // handleHexisAct — resolves entity references through Nexus and executes
 // matching capabilities through Hexis. Returns a reply string when handled,
 // or "" to fall through to the system command executor.
@@ -550,11 +608,11 @@ func (h *reactiveHandler) handleHexisAct(ctx context.Context, dec router.Decisio
 
 	// Resolve the utterance text as an entity reference through Nexus. An
 	// ambiguous match must stop and clarify — never guess a mutation target.
-	// The name comes from entityReferenceText, not straight from the Text slot:
-	// the model transliterates Latin names as it routes (Vikunja #476).
-	subject := entityReferenceText(dec)
+	// The names come from entityReferences, not straight from the Text slot: the
+	// model transliterates Latin names as it routes (Vikunja #476, #524).
 	started := h.now()
-	entityID, displayName, ambiguous, err := h.ecosystem.resolveEntityReference(ctx, subject, nil)
+	res := h.resolveEntityCandidates(ctx, entityReferences(dec))
+	subject, entityID, displayName, ambiguous, err := res.subject, res.entityID, res.displayName, res.ambiguous, res.err
 	if err != nil {
 		h.recordEcosystemTrace(ctx, "nexus", "resolve", traceStatusForError(err), started,
 			mergeFields(traceErrorFields(err), map[string]any{"subject": redactSubject(subject)}))