fix(insights): report every correlation through the significance gate

The /insights envelope (weight x BP, mood x BP, mood x weight, mood x
pulse, BP medication continuity) and the AI feature payload computed
their coefficients with an ungated Pearson that banded |r| above five
pairs, so five days of noise sloping the right way read as a strong
correlation there while every other surface refused the same points.
Both now use `significantPearsonCorrelation` (n >= 20 and p < 0.05,
through the engine's exact p-value), and the ungated function is gone.
The allowlist guard that tracked its remaining callers becomes a guard
that there is one Pearson implementation.

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

@@ -569,16 +569,10 @@ describe("GET /api/insights/comprehensive — envelope shape", () => {
     expect(body.data.moodSummary?.count).toBe(2);
   });
 
-  it("derives weight × BP scatter from daily-bucketed series", async () => {
-    vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
-    // Five day-aligned pairs (n >= 5 unlocks pearsonCorrelation).
-    const days = [
-      "2026-05-01",
-      "2026-05-02",
-      "2026-05-03",
-      "2026-05-04",
-      "2026-05-05",
-    ];
+  function mockWeightBpDays(count: number) {
+    const days = Array.from({ length: count }, (_, i) =>
+      new Date(Date.UTC(2026, 4, 1 + i)).toISOString().slice(0, 10),
+    );
     (buildComprehensiveAggregate as ReturnType<typeof vi.fn>).mockResolvedValue(
       {
         summaries: {},
@@ -592,22 +586,41 @@ describe("GET /api/insights/comprehensive — envelope shape", () => {
           })),
         },
         firstMeasurementAt: new Date(),
-        totalMeasurements: 10,
+        totalMeasurements: count * 2,
       },
     );
+  }
+
+  type WeightBpBody = {
+    data: {
+      scatterData: Array<{ weight: number; sysBP: number }>;
+      weightBpCorrelation: { r: number; n: number } | null;
+    };
+  };
+
+  it("derives weight × BP scatter from daily-bucketed series", async () => {
+    vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+    mockWeightBpDays(25);
 
     const res = await callGet(makeReq());
-    const body = (await res.json()) as {
-      data: {
-        scatterData: Array<{ weight: number; sysBP: number }>;
-        weightBpCorrelation: { r: number; n: number } | null;
-      };
-    };
-    expect(body.data.scatterData).toHaveLength(5);
+    const body = (await res.json()) as WeightBpBody;
+    expect(body.data.scatterData).toHaveLength(25);
     expect(body.data.scatterData[0]).toEqual({ weight: 80, sysBP: 120 });
-    // Perfect linear relationship → r === 1.
+    // Perfect linear relationship over 25 days → r === 1.
     expect(body.data.weightBpCorrelation?.r).toBe(1);
-    expect(body.data.weightBpCorrelation?.n).toBe(5);
+    expect(body.data.weightBpCorrelation?.n).toBe(25);
+  });
+
+  it("reports no correlation below the significance bar every surface uses", async () => {
+    // Five perfectly aligned days: the scatter shows them, but five points
+    // cannot carry a correlation (n >= 20 and p < 0.05).
+    vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+    mockWeightBpDays(5);
+
+    const res = await callGet(makeReq());
+    const body = (await res.json()) as WeightBpBody;
+    expect(body.data.scatterData).toHaveLength(5);
+    expect(body.data.weightBpCorrelation).toBeNull();
   });
 });
 
@@ -849,13 +862,10 @@ describe("GET /api/insights/comprehensive — mood × metric local-day pairing (
     // tier in R12. Both read the UTC `dailyByType` / UTC `scheduledFor`
     // slice, so their output must be invariant to the caller's timezone.
     // Run the SAME fixture under UTC then America/New_York and deep-equal.
-    const days = [
-      "2026-05-01",
-      "2026-05-02",
-      "2026-05-03",
-      "2026-05-04",
-      "2026-05-05",
-    ];
+    // 25 days: a correlation has to clear n >= 20 and p < 0.05 to exist.
+    const days = Array.from({ length: 25 }, (_, i) =>
+      new Date(Date.UTC(2026, 4, 1 + i)).toISOString().slice(0, 10),
+    );
     const aggregate = {
       summaries: {},
       bpRawRows: { sys: [], dia: [] },
@@ -896,20 +906,20 @@ describe("GET /api/insights/comprehensive — mood × metric local-day pairing (
       scheduleRevisions: [],
       pauseEras: [],
     };
-    // Intake taken on the first three days, logged as skipped on the last
-    // two → a non-degenerate continuity series. The skips used to be absent
+    // Intake taken on the first fifteen days, logged as skipped on the
+    // last ten → a non-degenerate continuity series. The skips used to be absent
     // rows: a day with no record read as a measured 0 % continuity, which is
     // the fabrication the route no longer makes, and a fixture that relies on
     // it would be pinning the defect rather than the timezone question this
-    // test asks. Recording the two days as skips keeps five paired days AND
+    // test asks. Recording the days as skips keeps every day paired AND
     // keeps every one of them a thing the person actually logged.
     const intakeEvents = days.map((d, i) => ({
       medicationId: "med-bp",
       userId: "user-comp-1",
       deletedAt: null,
       scheduledFor: new Date(`${d}T07:00:00Z`),
-      takenAt: i < 3 ? new Date(`${d}T07:05:00Z`) : null,
-      skipped: i >= 3,
+      takenAt: i < 15 ? new Date(`${d}T07:05:00Z`) : null,
+      skipped: i >= 15,
     }));
 
     function primeMocks() {
@@ -948,7 +958,8 @@ describe("GET /api/insights/comprehensive — mood × metric local-day pairing (
     );
     // And the guard is meaningful only if these joins actually produced
     // output to compare.
-    expect(utcBody.data.scatterData).toHaveLength(5);
+    expect(utcBody.data.scatterData).toHaveLength(25);
+    expect(utcBody.data.weightBpCorrelation).not.toBeNull();
     expect(utcBody.data.bpMedicationCorrelation).not.toBeNull();
   });
 });

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

@@ -12,7 +12,7 @@ import {
   generateAlerts,
 } from "@/lib/analytics/classifications";
 import {
-  pearsonCorrelation,
+  significantPearsonCorrelation,
   type PairedPoint,
 } from "@/lib/analytics/correlations";
 import {
@@ -285,7 +285,7 @@ export async function buildComprehensiveResponse(user: AuthedUser) {
   const weightDaily = aggregate.dailyByType.WEIGHT ?? [];
   const sysDaily = aggregate.dailyByType.BLOOD_PRESSURE_SYS ?? [];
   const weightBpPairs: PairedPoint[] = joinDailyByDay(weightDaily, sysDaily);
-  const weightBpCorrelation = pearsonCorrelation(weightBpPairs);
+  const weightBpCorrelation = significantPearsonCorrelation(weightBpPairs);
   const scatterData = weightBpPairs.map((p) => ({
     weight: p.a,
     sysBP: p.b,
@@ -308,11 +308,11 @@ export async function buildComprehensiveResponse(user: AuthedUser) {
   );
 
   const moodBpPairs = pairMoodWithDaily(dailyMoodEntries, sysDailyLocal);
-  const moodBpCorrelation = pearsonCorrelation(moodBpPairs);
+  const moodBpCorrelation = significantPearsonCorrelation(moodBpPairs);
   const moodBpScatterData = moodBpPairs.map((p) => ({ mood: p.a, sysBP: p.b }));
 
   const moodWeightPairs = pairMoodWithDaily(dailyMoodEntries, weightDailyLocal);
-  const moodWeightCorrelation = pearsonCorrelation(moodWeightPairs);
+  const moodWeightCorrelation = significantPearsonCorrelation(moodWeightPairs);
   const moodWeightScatterData = moodWeightPairs.map((p) => ({
     mood: p.a,
     weight: p.b,
@@ -374,7 +374,7 @@ export async function buildComprehensiveResponse(user: AuthedUser) {
     .sort(([a], [b]) => a.localeCompare(b))
     .map(([day, stats]) => ({ day, value: stats.sum / stats.count }));
   const moodPulsePairs = pairMoodWithDaily(dailyMoodEntries, restingPulseDaily);
-  const moodPulseCorrelation = pearsonCorrelation(moodPulsePairs);
+  const moodPulseCorrelation = significantPearsonCorrelation(moodPulsePairs);
   const moodPulseScatterData = moodPulsePairs.map((p) => ({
     mood: p.a,
     pulse: p.b,
@@ -558,7 +558,7 @@ export async function buildComprehensiveResponse(user: AuthedUser) {
       });
     }
 
-    const corr = pearsonCorrelation(pairs);
+    const corr = significantPearsonCorrelation(pairs);
     if (corr) {
       bpMedicationCorrelation = {
         ...corr,
@@ -667,7 +667,7 @@ function deriveDailyLocalMeans(
 
 /**
  * Daily-key inner join between two daily-aggregated series. Returns
- * `PairedPoint` shapes compatible with `pearsonCorrelation`.
+ * `PairedPoint` shapes compatible with `significantPearsonCorrelation`.
  *
  * Inputs are sorted ASC by `day` (the aggregator's ORDER BY
  * guarantees that). The walk is O(n + m) merge-join style instead of