fix(labs): never present a converted reading's printed range in the wrong unit

A converted reading's bounds move with its value, but the printed range text
stays in the unit the report used, and every reader preferred that text: the
list showed "Report range 3.9 to 5.5" beside 100.9 mg/dL, and the doctor
report and the FHIR referenceRange.text did the same. The text is still
stored verbatim. The range resolver now takes the reading's sourceUnit (as a
required field, so no reader can forget to select it) and, for a converted
reading, leaves the window's text empty so every surface states the converted
bounds in the marker's unit, and hands the printed text over separately with
its unit. The lab DTO carries it as printedReferenceText, and the note beside
a reading shows it as "as printed in mmol/L: ...".

tests/integration/lab-source-reference-range.test.ts

@@ -225,6 +225,78 @@ describe("a printed reference range, end to end", () => {
     });
   });
 
+  it("keeps a converted reading's printed text as evidence, never as the window of the converted value", async () => {
+    const prisma = getPrismaClient();
+    // A glucose marker tracked in mg/dL; the report prints mmol/L.
+    const marker = await prisma.biomarker.create({
+      data: {
+        userId: USER_ID,
+        name: "Glucose",
+        unit: "mg/dL",
+        lowerBound: 70,
+        upperBound: 100,
+      },
+    });
+    const PRINTED_MMOL = "3,9 - 5,5 mmol/l";
+    const { POST } = await import("@/app/api/labs/route");
+    const res = await POST(
+      postReq({
+        biomarkerId: marker.id,
+        value: 5.6,
+        unit: "mmol/L",
+        sourceReferenceLow: 3.9,
+        sourceReferenceHigh: 5.5,
+        sourceReferenceText: PRINTED_MMOL,
+        takenAt: "2026-07-03T08:00:00.000Z",
+      }),
+    );
+    expect(res.status).toBe(201);
+
+    // The record keeps what the report printed, verbatim.
+    const row = await prisma.labResult.findFirstOrThrow({
+      where: { userId: USER_ID },
+    });
+    expect(row.sourceReferenceText).toBe(PRINTED_MMOL);
+    expect(row.sourceUnit).toBe("mmol/L");
+
+    // The DTO states the window in force in mg/dL only, and hands the printed
+    // text over separately, beside the unit it is in.
+    const dto = await readDto("Glucose");
+    expect(dto.converted).toBe(true);
+    expect(dto.unit).toBe("mg/dL");
+    expect(dto.referenceOrigin).toBe("source");
+    expect(dto.referenceLow).toBeCloseTo(3.9 * 18.0182, 6);
+    expect(dto.referenceHigh).toBeCloseTo(5.5 * 18.0182, 6);
+    expect(dto.sourceReferenceText).toBeNull();
+    expect(dto.printedReferenceText).toBe(PRINTED_MMOL);
+    expect(dto.sourceUnit).toBe("mmol/L");
+
+    // The doctor report has no mmol/L text to print beside mg/dL numbers.
+    const { loadLabResults } =
+      await import("@/lib/doctor-report/clinical-records");
+    const labs = await loadLabResults(
+      USER_ID,
+      new Date("2026-01-01T00:00:00.000Z"),
+      new Date("2026-12-31T23:59:59.000Z"),
+    );
+    expect(labs?.[0].sourceReferenceText).toBeNull();
+    expect(labs?.[0].referenceLow).toBeCloseTo(3.9 * 18.0182, 6);
+
+    // FHIR: the text, when present, must agree with low and high. Here it is
+    // left out, and the bounds carry the marker's unit like the value.
+    const { labObservations } = await import("@/lib/fhir/resources/labs");
+    let seq = 0;
+    const observations = labObservations(
+      { labResults: labs } as Parameters<typeof labObservations>[0],
+      () => `obs-${++seq}`,
+    );
+    const range = observations[0].referenceRange?.[0];
+    expect(range?.text).toBeUndefined();
+    expect(range?.low?.unit).toBe("mg/dL");
+    expect(range?.high?.value).toBeCloseTo(5.5 * 18.0182, 6);
+    expect(observations[0].valueQuantity?.unit).toBe("mg/dL");
+  });
+
   it("keeps a window it cannot read as text and leaves the catalog in force", async () => {
     const prisma = getPrismaClient();
     await seedMarker();