Add 3-Day Outlook generation

internal/app/app_test.go

@@ -523,6 +523,81 @@ func TestTomorrowReportCanCompareAgainstPriorDailySnapshot(t *testing.T) {
 	}
 }
 
+func TestGenerateThreeDayReportWritesReportAndRecentChanges(t *testing.T) {
+	server := dailyBundleServer(t)
+	cfg := config.Defaults()
+	cfg.WeatherAPI.BaseURL = server.URL + "/"
+	cfg.WeatherAPI.Timezone = "America/Chicago"
+	cfg.Workspace.Root = t.TempDir()
+	store, err := state.NewFilesystemStore(cfg.Workspace)
+	if err != nil {
+		t.Fatalf("NewFilesystemStore() error = %v", err)
+	}
+	priorResolved, err := ResolveGenerate(GenerateRequest{
+		Config: cfg,
+		Report: ReportThreeDay,
+	}, mustParse("2026-05-29T04:00:00-05:00"))
+	if err != nil {
+		t.Fatalf("ResolveGenerate(prior) error = %v", err)
+	}
+	priorBriefing := priorThreeDayBriefing(priorResolved)
+	priorBriefingPath, err := store.SaveBriefing(context.Background(), priorResolved, priorBriefing)
+	if err != nil {
+		t.Fatalf("SaveBriefing() error = %v", err)
+	}
+	priorPaths, err := store.Paths(priorResolved)
+	if err != nil {
+		t.Fatalf("Paths() error = %v", err)
+	}
+	_, err = store.SaveMetadata(context.Background(), state.BuildMetadata(priorResolved, priorBriefing, state.ArtifactPaths{
+		Briefing:       priorBriefingPath,
+		DataPackage:    priorPaths.DataPackage,
+		Preflight:      priorPaths.Preflight,
+		RenderedReport: priorPaths.RenderedReport,
+	}))
+	if err != nil {
+		t.Fatalf("SaveMetadata() error = %v", err)
+	}
+	currentResolved, err := ResolveGenerate(GenerateRequest{
+		Config: cfg,
+		Report: ReportThreeDay,
+	}, mustParse("2026-05-29T05:00:00-05:00"))
+	if err != nil {
+		t.Fatalf("ResolveGenerate(current) error = %v", err)
+	}
+	renderer := &recordingRenderer{
+		renderResult: &scriptorium.RenderResult{ExitCode: 0},
+		runResult:    &scriptorium.RunResult{ExitCode: 0},
+		runBody:      "# 3-Day Outlook\n",
+	}
+
+	result, err := GenerateReport(context.Background(), ReportRequest{
+		Config:   cfg,
+		Resolved: currentResolved,
+		Renderer: renderer,
+		Store:    store,
+	})
+	if err != nil {
+		t.Fatalf("GenerateReport() error = %v", err)
+	}
+
+	if result.Briefing.ThreeDay == nil {
+		t.Fatal("ThreeDay = nil")
+	}
+	if len(result.Briefing.ThreeDay.Days) != 3 {
+		t.Fatalf("ThreeDay days = %d, want 3", len(result.Briefing.ThreeDay.Days))
+	}
+	if renderer.renderRequest.PromptID != "weather.three_day_outlook" {
+		t.Fatalf("render PromptID = %q, want weather.three_day_outlook", renderer.renderRequest.PromptID)
+	}
+	if result.PriorSnapshot == nil {
+		t.Fatal("PriorSnapshot = nil, want prior 3-day snapshot")
+	}
+	if len(result.RecentChanges) == 0 {
+		t.Fatal("RecentChanges length = 0, want changes from prior 3-day snapshot")
+	}
+}
+
 func TestResolveGenerateMapsCommandToReportDefinition(t *testing.T) {
 	cfg := config.Defaults()
 	cfg.WeatherAPI.Timezone = "America/Chicago"
@@ -652,6 +727,35 @@ func priorDailyBriefing(resolved report.Resolved) briefing.Package {
 	}
 }
 
+func priorThreeDayBriefing(resolved report.Resolved) briefing.Package {
+	high := 58.0
+	precip := 10.0
+	return briefing.Package{
+		Metadata: briefing.Metadata{
+			SchemaVersion: briefing.SchemaVersion,
+			RunID:         resolved.Metadata().RunID,
+			ReportID:      resolved.Definition.ID,
+			PromptID:      resolved.Definition.PromptID,
+			GeneratedAt:   resolved.GeneratedAt,
+			Units:         "us",
+			Timezone:      resolved.Timezone,
+			ValidPeriod:   resolved.ValidPeriod,
+		},
+		ThreeDay: &briefing.ThreeDay{
+			Days: []briefing.OutlookDay{
+				{
+					Date:        "2026-05-29",
+					Temperature: forecast.Range{Max: &high},
+					MaxPrecipitationProbability: &forecast.TimedValue{
+						Value: precip,
+						Time:  resolved.ValidPeriod.Start.Add(6 * time.Hour),
+					},
+				},
+			},
+		},
+	}
+}
+
 type recordingRenderer struct {
 	renderCalls   int
 	runCalls      int