docs(import): put a contextless sensor reading in the downloadable example

The example CSV is the file people copy. It showed a glucose row with a
FASTING context and nothing else, which is the shape a meter produces, not
the shape a continuous sensor produces. It now carries both.

Refs #640

src/components/settings/__tests__/import-panel.test.tsx

@@ -152,6 +152,18 @@ describe("EXAMPLE_CSV", () => {
     expect(out.rows.length).toBeGreaterThan(0);
     expect(out.rows.every((r) => r.status === "ok")).toBe(true);
   });
+
+  it("carries a contextless glucose reading, the shape a sensor export has", () => {
+    const out = parseCsvMeasurements(EXAMPLE_CSV, {
+      now: new Date("2026-06-01T00:00:00Z").getTime(),
+    });
+    const glucose = out.rows
+      .map((r) => r.row)
+      .filter((row) => row?.type === "BLOOD_GLUCOSE");
+    expect(glucose.length).toBeGreaterThanOrEqual(2);
+    expect(glucose.some((row) => row?.glucoseContext === undefined)).toBe(true);
+    expect(glucose.some((row) => row?.glucoseContext === "FASTING")).toBe(true);
+  });
 });
 
 describe("parseImportJson guard", () => {

src/components/settings/import-panel/import-examples.ts

@@ -64,5 +64,9 @@ export const EXAMPLE_CSV = [
   CSV_EXAMPLE_COLUMNS.join(","),
   "WEIGHT,80.5,kg,2026-05-01T08:00:00Z,,morning,",
   "BLOOD_GLUCOSE,5.3,mmol/L,2026-05-01T08:05:00+02:00,FASTING,,meter-001",
+  // A sensor export has no fasting / post-meal answer per reading, so the
+  // context cell is blank. The example carries that shape on purpose: it is
+  // the one people copy, and it is the case that used to be refused.
+  "BLOOD_GLUCOSE,5.9,mmol/L,2026-05-01T08:20:00+02:00,,,sensor-001",
   "BLOOD_PRESSURE_SYS,120,mmHg,2026-05-01T08:05:00+02:00,,,",
 ].join("\n");