Fix entities not showing due to JavaScript crash (fixes #25363) (#26599)

* Fix entity UI crash from undefined entity names (fixes #25363)

* Fix mock function type compatibility in test

- Update mock to handle string | undefined parameter
- Maintain test functionality while satisfying type checker

* Simplify approach based on reviewer feedback

- Use String() coercion to preserve numeric entity names (e.g., power strip outlets)
- Single line change instead of complex type validation across multiple files
- Revert stripPrefixFromEntityName to original (no longer needs null handling)
- Remove separate test file, update existing test to expect stringified numbers
- More conservative approach that preserves data rather than replacing with fallbacks

test/common/entity/compute_entity_name.test.ts

@@ -134,4 +134,29 @@ describe("computeEntityEntryName", () => {
     };
     expect(computeEntityEntryName(entry as any, hass as any)).toBeUndefined();
   });
+
+  it("handles entities with numeric original_name (real bug from issue #25363)", () => {
+    vi.spyOn(computeDeviceNameModule, "computeDeviceName").mockReturnValue(
+      "Texas Instruments CC2652"
+    );
+
+    const entry = {
+      entity_id: "sensor.texas_instruments_cc2652_2",
+      name: null, // null name
+      original_name: 2, // Number instead of string! This caused the original crash
+      device_id: "dev1",
+      has_entity_name: true,
+    };
+    const hass = {
+      devices: { dev1: {} },
+      states: {},
+    };
+
+    // Should not throw an error and should return the stringified number
+    expect(() =>
+      computeEntityEntryName(entry as any, hass as any)
+    ).not.toThrow();
+    expect(computeEntityEntryName(entry as any, hass as any)).toBe("2");
+    vi.restoreAllMocks();
+  });
 });