refactor(core): normalize core service naming

Standardize core service module and export names to reduce naming ambiguity and make imports predictable across runtime, tests, scripts, and docs.

src/core/services/overlay-content-measurement.test.ts

@@ -0,0 +1,87 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+
+import {
+  createOverlayContentMeasurementStore,
+  sanitizeOverlayContentMeasurement,
+} from "./overlay-content-measurement";
+
+test("sanitizeOverlayContentMeasurement accepts valid payload with null rect", () => {
+  const measurement = sanitizeOverlayContentMeasurement(
+    {
+      layer: "visible",
+      measuredAtMs: 100,
+      viewport: { width: 1920, height: 1080 },
+      contentRect: null,
+    },
+    500,
+  );
+
+  assert.deepEqual(measurement, {
+    layer: "visible",
+    measuredAtMs: 100,
+    viewport: { width: 1920, height: 1080 },
+    contentRect: null,
+  });
+});
+
+test("sanitizeOverlayContentMeasurement rejects invalid ranges", () => {
+  const measurement = sanitizeOverlayContentMeasurement(
+    {
+      layer: "invisible",
+      measuredAtMs: 100,
+      viewport: { width: 0, height: 1080 },
+      contentRect: { x: 0, y: 0, width: 100, height: 20 },
+    },
+    500,
+  );
+
+  assert.equal(measurement, null);
+});
+
+test("overlay measurement store keeps latest payload per layer", () => {
+  const store = createOverlayContentMeasurementStore({
+    now: () => 1000,
+    warn: () => {
+      // noop
+    },
+  });
+
+  const visible = store.report({
+    layer: "visible",
+    measuredAtMs: 900,
+    viewport: { width: 1280, height: 720 },
+    contentRect: { x: 50, y: 60, width: 400, height: 80 },
+  });
+  const invisible = store.report({
+    layer: "invisible",
+    measuredAtMs: 910,
+    viewport: { width: 1280, height: 720 },
+    contentRect: { x: 20, y: 30, width: 300, height: 40 },
+  });
+
+  assert.equal(visible?.layer, "visible");
+  assert.equal(invisible?.layer, "invisible");
+  assert.equal(store.getLatestByLayer("visible")?.contentRect?.width, 400);
+  assert.equal(store.getLatestByLayer("invisible")?.contentRect?.height, 40);
+});
+
+test("overlay measurement store rate-limits invalid payload warnings", () => {
+  let now = 1_000;
+  const warnings: string[] = [];
+  const store = createOverlayContentMeasurementStore({
+    now: () => now,
+    warn: (message) => {
+      warnings.push(message);
+    },
+  });
+
+  store.report({ layer: "visible" });
+  store.report({ layer: "visible" });
+  assert.equal(warnings.length, 0);
+
+  now = 11_000;
+  store.report({ layer: "visible" });
+  assert.equal(warnings.length, 1);
+  assert.match(warnings[0], /Dropped 3 invalid measurement payload/);
+});