feat(insights): make each person-defined symptom its own correlation channel

Every active symptom definition enters pattern discovery as an outcome
channel SYMPTOM:<id>, labelled with its decrypted name (the data label
the interpretation already prefers over the key). The daily value is the
day's highest intensity in the person's zone; days without an occurrence
count as 0 only between the first and the last logged day. At most eight,
the active-definition cap. The SYMPTOM: prefix resolves to the illness
module in the surface map, so the family leaves the matrix with the
module, and the discovery guard lists the new fetcher.

src/app/api/insights/correlations/__tests__/route.test.ts

@@ -31,6 +31,7 @@ vi.mock("@/lib/db", () => ({
     // channel produces a point.
     environmentContext: { findMany: vi.fn().mockResolvedValue([]) },
     customMetric: { findMany: vi.fn().mockResolvedValue([]) },
+    symptomDefinition: { findMany: vi.fn().mockResolvedValue([]) },
   },
 }));
 
@@ -153,6 +154,7 @@ beforeEach(() => {
     prisma.environmentContext.findMany as ReturnType<typeof vi.fn>
   ).mockResolvedValue([]);
   vi.mocked(prisma.customMetric.findMany).mockResolvedValue([] as never);
+  vi.mocked(prisma.symptomDefinition.findMany).mockResolvedValue([] as never);
 });
 
 const callGet = GET as unknown as (req: NextRequest) => Promise<Response>;

src/app/api/insights/correlations/route.ts

@@ -236,6 +236,7 @@ async function buildCorrelationsResponse(
       // available for the scan.
       environment_days: diagnostics.environmentDays,
       custom_metric_channels: diagnostics.customMetricChannels,
+      symptom_event_channels: diagnostics.symptomEventChannels,
       custom_metric_days: diagnostics.customMetricDays,
     },
   });