fix(cortex): update date handling in API and UI components

- Adjusted date handling in the agenda API to ensure optional parameters for start, end, and label are correctly processed.
- Enhanced chat input and action parser to support optional date labels for relative dates.
- Updated agenda components to handle date ranges and loading states more effectively.
- Improved error handling and loading indicators in the agenda block for better user experience.

This commit ensures consistency in date handling across the application, aligning with the new requirements for relative date inputs.

components/cortex/artifacts/artifact-container.tsx

@@ -19,6 +19,7 @@ import { PatientDashboardBlock } from '../blocks/patient-dashboard-block';
 import { FallbackPicker } from '../blocks/fallback-picker';
 import { APPOINTMENT_TYPES, type AppointmentTypeCode, type LocationClassCode } from '@/app/epd/agenda/types';
 import type { Artifact, BlockType } from '@/stores/cortex-store';
+import { parseRelativeDate, isDateRange } from '@/lib/cortex/date-time-parser';
 
 interface ArtifactContainerProps {
   artifacts: Artifact[];
@@ -55,13 +56,13 @@ function coerceDate(value: unknown): Date | undefined {
 }
 
 function coerceDateRange(raw: any): AgendaBlockProps['dateRange'] | undefined {
-  const start = coerceDate(raw?.start);
-  const end = coerceDate(raw?.end);
-  if (!start || !end) return undefined;
+  const label = typeof raw?.label === 'string' ? raw.label : undefined;
+  if (!label) return undefined;
+
   return {
-    start,
-    end,
-    label: typeof raw?.label === 'string' ? raw.label : 'custom',
+    start: coerceDate(raw?.start),
+    end: coerceDate(raw?.end),
+    label,
   };
 }
 
@@ -78,6 +79,21 @@ function resolveLocation(value: unknown): LocationClassCode | undefined {
   return undefined;
 }
 
+/**
+ * Convert date label to Date using central date-time-parser (DRY)
+ */
+function resolveDateFromLabel(label?: string): Date | null {
+  if (!label) return null;
+
+  const parsed = parseRelativeDate(label);
+  if (!parsed) return null;
+
+  // DateRange → return start date
+  if (isDateRange(parsed)) return parsed.start;
+
+  return parsed;
+}
+
 function buildAgendaPrefill(prefill: Record<string, any> | undefined): AgendaBlockProps['prefillData'] {
   if (!prefill || typeof prefill !== 'object') return undefined;
 
@@ -90,9 +106,15 @@ function buildAgendaPrefill(prefill: Record<string, any> | undefined): AgendaBlo
         }
       : undefined);
 
+  // Try to resolve date from label first (more reliable than AI-generated dates)
+  const dateLabel = prefill?.datetime?.label || prefill?.dateRange?.label;
+  const resolvedDate = resolveDateFromLabel(dateLabel);
+  
   const datetimeDate =
+    resolvedDate ||  // Prefer calculated date from label
     coerceDate(prefill?.datetime?.date) ||
     (prefill?.datetime?.time ? new Date() : undefined);
+    
   const datetime = datetimeDate
     ? {
         date: datetimeDate,
@@ -103,7 +125,12 @@ function buildAgendaPrefill(prefill: Record<string, any> | undefined): AgendaBlo
   const appointmentType = resolveAppointmentType(prefill?.appointmentType || prefill?.type);
   const location = resolveLocation(prefill?.location);
 
+  // Also resolve newDatetime from label
+  const newDateLabel = prefill?.newDatetime?.label;
+  const resolvedNewDate = resolveDateFromLabel(newDateLabel);
+  
   const newDatetimeDate =
+    resolvedNewDate ||  // Prefer calculated date from label
     coerceDate(prefill?.newDatetime?.date) ||
     (prefill?.newDatetime?.time ? new Date() : undefined);
   const newDatetime = newDatetimeDate