fix: deliver validated AI insight responses

internal/growthreport/model.go

@@ -33,8 +33,14 @@ type CampaignBrief struct {
 	EvidenceIDs       []string `json:"evidenceIds"`
 }
 
+type EventRecommendation struct {
+	EvidenceID      string `json:"evidenceId"`
+	RelevanceReason string `json:"relevanceReason"`
+}
+
 type AICopy struct {
-	Briefs []CampaignBrief `json:"briefs"`
+	EventRecommendations []EventRecommendation `json:"eventRecommendations"`
+	Briefs               []CampaignBrief       `json:"briefs,omitempty"`
 }
 
 type Usage struct {
@@ -53,7 +59,7 @@ type Report struct {
 	Status                Status          `json:"status"`
 	Scope                 Scope           `json:"scope"`
 	HorizonDays           int             `json:"horizonDays"`
-	ForecastStartDate     *time.Time      `json:"forecastStartDate,omitempty"`
+	ForecastStartDate     *time.Time      `json:"-"`
 	DeterministicEvidence json.RawMessage `json:"deterministicEvidence,omitempty"`
 	AICopy                *AICopy         `json:"aiCopy,omitempty"`
 	FailureCode           *string         `json:"failureCode,omitempty"`