feat: add priority demotion controls

apps/api/internal/store/rate_limit_status_test.go

@@ -1,6 +1,9 @@
 package store
 
-import "testing"
+import (
+	"testing"
+	"time"
+)
 
 func TestEffectiveModelRateLimitPolicyTreatsModelRulesAsAuthoritative(t *testing.T) {
 	policy := effectiveModelRateLimitPolicy(
@@ -30,3 +33,31 @@ func TestEffectiveModelRateLimitPolicyTreatsModelRulesAsAuthoritative(t *testing
 		t.Fatalf("expected missing model tpm limit to mean unlimited, got %v", got)
 	}
 }
+
+func TestPriorityDemotionRecordFromEventPayloadKeepsReason(t *testing.T) {
+	createdAt := time.Date(2026, 5, 12, 9, 30, 0, 0, time.UTC)
+	record := priorityDemotionRecordFromEventPayload("event-1", "task-1", "fallback message", map[string]any{
+		"platformId":      "platform-1",
+		"platformModelId": "platform-model-1",
+		"reason":          "priority_demote_policy",
+		"errorCode":       "rate_limit",
+		"errorMessage":    "upstream 429 rate limit",
+		"category":        "rate_limit",
+		"statusCode":      float64(429),
+		"policySource":    "gateway_runner_policies.priority_demote_policy",
+		"policy":          "priorityDemotePolicy",
+		"policyRule":      "categories",
+		"matchedValue":    "rate_limit",
+		"dynamicPriority": float64(1511),
+	}, createdAt)
+
+	if record.Reason != "priority_demote_policy" || record.ErrorMessage != "upstream 429 rate limit" {
+		t.Fatalf("expected demotion reason and error message to survive, got %+v", record)
+	}
+	if record.StatusCode != 429 || record.DynamicPriority != 1511 {
+		t.Fatalf("expected numeric demotion metadata, got %+v", record)
+	}
+	if !record.CreatedAt.Equal(createdAt) {
+		t.Fatalf("expected createdAt %s, got %s", createdAt, record.CreatedAt)
+	}
+}