test(measurements): cover the unit transform, MCP unit hardening, and a display guard

Add affine-correctness tests for the transform registry (°C→°F absolute vs a
delta that must stay offset-free, lb/in factors, inverse round-trips), a
resolver test for the inbound unit aliases, a preferred-unit entry-form label
test, and MCP cases for converting a lb hint to canonical kg and refusing an
unknown unit. Add the structural guard that trips if any dashboard or insight
surface reintroduces a hardcoded transformed-type unit or value scale. Ship the
diagnose/convert script pair for legacy non-canonical measurement rows.

src/components/measurements/__tests__/measurement-form-unit-label.test.tsx

@@ -0,0 +1,66 @@
+import { describe, expect, it, vi } from "vitest";
+import { renderToStaticMarkup } from "react-dom/server";
+
+/**
+ * v1.32.26 (issue #627) — the manual entry form labels its value field in the
+ * user's preferred unit for a type with a metric/imperial transform. A metric
+ * user sees "kg"; an imperial user sees "lb". The field is the entry boundary
+ * that converts the typed number back to canonical SI on submit, so the label
+ * and the stored unit must agree with the preference.
+ */
+
+let preference: "metric" | "imperial" = "metric";
+
+vi.mock("@/hooks/use-auth", () => ({
+  useAuth: () => ({
+    user: {
+      id: "u1",
+      username: "testuser",
+      role: "USER",
+      unitPreference: preference,
+    },
+    isAuthenticated: true,
+    isLoading: false,
+  }),
+}));
+
+vi.mock("@tanstack/react-query", () => ({
+  useQueryClient: () => ({
+    invalidateQueries: vi.fn(),
+    refetchQueries: vi.fn(),
+  }),
+}));
+
+vi.mock("@/lib/api/api-fetch", () => ({
+  apiPost: vi.fn().mockResolvedValue({}),
+}));
+
+import { I18nProvider } from "@/lib/i18n/context";
+import { MeasurementForm } from "../measurement-form";
+
+function render(): string {
+  return renderToStaticMarkup(
+    <I18nProvider initialLocale="en">
+      <MeasurementForm defaultType="WEIGHT" />
+    </I18nProvider>,
+  );
+}
+
+describe("MeasurementForm — preferred-unit value label", () => {
+  it("labels the weight field in kg for a metric user", () => {
+    preference = "metric";
+    const html = render();
+    expect(html).toContain("kg");
+    expect(html).not.toContain("lb");
+    // The metric placeholder (kg) is shown, not the imperial one.
+    expect(html).toContain('placeholder="75.5"');
+  });
+
+  it("labels the weight field in lb for an imperial user", () => {
+    preference = "imperial";
+    const html = render();
+    expect(html).toContain("lb");
+    // The imperial placeholder (lb) is shown.
+    expect(html).toContain('placeholder="165"');
+  });
+});