Stop substituting synthetic market data when providers fail

- Replace synthetic fallback in getQuote()/getPriceHistory() with null returns
- Add QuoteResult/PriceHistoryResult types with { value, stale } structure
- Implement stale-while-revalidate: return cached value with stale=true on live fetch failure
- Cache failures for 30s to avoid hammering provider
- Update CompanyAnalysis type to use PriceData<T> wrapper
- Update task-processors to track failed/stale tickers explicitly
- Update price-history-card UI to show unavailable state and stale indicator
- Add comprehensive tests for failure cases
- Add e2e tests for null data, stale data, and live data scenarios

Resolves #14

components/analysis/price-history-card.tsx

@@ -4,13 +4,13 @@ import { format } from 'date-fns';
 import { Panel } from '@/components/ui/panel';
 import { formatCurrency } from '@/lib/format';
 import { InteractivePriceChart } from '@/components/charts/interactive-price-chart';
-import type { DataSeries, Holding } from '@/lib/types';
+import type { DataSeries, Holding, PriceData } from '@/lib/types';
 
 type PriceHistoryCardProps = {
   loading: boolean;
-  priceHistory: Array<{ date: string; close: number }>;
-  benchmarkHistory: Array<{ date: string; close: number }>;
-  quote: number;
+  priceHistory: PriceData<Array<{ date: string; close: number }> | null>;
+  benchmarkHistory: PriceData<Array<{ date: string; close: number }> | null>;
+  quote: PriceData<number | null>;
   position: Holding | null;
 };
 
@@ -29,9 +29,14 @@ function asFiniteNumber(value: string | number | null | undefined) {
 }
 
 export function PriceHistoryCard(props: PriceHistoryCardProps) {
-  const firstPoint = props.priceHistory[0];
-  const lastPoint = props.priceHistory[props.priceHistory.length - 1];
+  const priceHistoryValue = props.priceHistory.value;
+  const benchmarkHistoryValue = props.benchmarkHistory.value;
+  const quoteValue = props.quote.value;
+
+  const firstPoint = priceHistoryValue?.[0];
+  const lastPoint = priceHistoryValue?.[priceHistoryValue.length - 1];
   const inPortfolio = props.position !== null;
+  const hasPriceData = priceHistoryValue !== null && priceHistoryValue.length > 0;
 
   const defaultChange = firstPoint && lastPoint ? lastPoint.close - firstPoint.close : null;
   const defaultChangePct = firstPoint && firstPoint.close > 0 && defaultChange !== null
@@ -54,10 +59,16 @@ export function PriceHistoryCard(props: PriceHistoryCardProps) {
   const statusToneClass = inPortfolio ? 'text-[#96f5bf]' : 'text-[color:var(--terminal-bright)]';
   const performanceToneClass = change !== null && change < 0 ? 'text-[#ff9f9f]' : 'text-[#96f5bf]';
 
-  const chartData = props.priceHistory.map(point => ({
+  const chartData = priceHistoryValue?.map(point => ({
     date: point.date,
     price: point.close
-  }));
+  })) ?? [];
+
+  const benchmarkData = benchmarkHistoryValue?.map((point) => ({
+    date: point.date,
+    price: point.close
+  })) ?? [];
+
   const comparisonSeries: DataSeries[] = [
     {
       id: 'stock',
@@ -69,22 +80,28 @@ export function PriceHistoryCard(props: PriceHistoryCardProps) {
     {
       id: 'sp500',
       label: 'S&P 500',
-      data: props.benchmarkHistory.map((point) => ({
-        date: point.date,
-        price: point.close
-      })),
+      data: benchmarkData,
       color: '#8ba0b8',
       type: 'line'
     }
   ];
 
-  const helperText = Number.isFinite(props.quote)
-    ? `Spot price ${formatCurrency(props.quote)}`
+  const quoteAvailable = quoteValue !== null && Number.isFinite(quoteValue);
+  const staleIndicator = props.quote.stale ? ' (stale)' : '';
+  const helperText = quoteAvailable
+    ? `Spot price ${formatCurrency(quoteValue)}${staleIndicator}`
     : 'Spot price unavailable';
 
   return (
-    <Panel title="Price chart" subtitle="Interactive chart with historical data">
+    <Panel title="Price chart" subtitle={hasPriceData ? 'Interactive chart with historical data' : 'Price data unavailable'}>
       <div className="space-y-4">
+        {!hasPriceData && (
+          <div className="rounded border border-[color:var(--line-weak)] bg-[color:var(--surface-dim)] px-4 py-3">
+            <p className="text-sm text-[color:var(--terminal-muted)]">
+              Price history data is currently unavailable. This may be due to a temporary issue with the market data provider.
+            </p>
+          </div>
+        )}
         <div className="grid grid-cols-1 gap-4 sm:grid-cols-3">
           <div className="border-b border-[color:var(--line-weak)] px-4 py-4 sm:border-b-0 sm:border-r">
             <p className="text-xs uppercase tracking-[0.14em] text-[color:var(--terminal-muted)]">Portfolio status</p>
@@ -108,20 +125,22 @@ export function PriceHistoryCard(props: PriceHistoryCardProps) {
           </div>
         </div>
 
-        <InteractivePriceChart
-          data={chartData}
-          dataSeries={comparisonSeries}
-          defaultChartType="line"
-          defaultTimeRange="1Y"
-          showVolume={false}
-          showToolbar={true}
-          height={320}
-          loading={props.loading}
-          formatters={{
-            price: formatCurrency,
-            date: (date: string) => format(new Date(date), 'MMM dd, yyyy')
-          }}
-        />
+        {hasPriceData && (
+          <InteractivePriceChart
+            data={chartData}
+            dataSeries={comparisonSeries}
+            defaultChartType="line"
+            defaultTimeRange="1Y"
+            showVolume={false}
+            showToolbar={true}
+            height={320}
+            loading={props.loading}
+            formatters={{
+              price: formatCurrency,
+              date: (date: string) => format(new Date(date), 'MMM dd, yyyy')
+            }}
+          />
+        )}
       </div>
     </Panel>
   );