feat: enhance habit tracking with pending state management and history refresh

src/App.test.tsx

@@ -282,7 +282,7 @@ describe("homepage", () => {
     await act(async () => container.querySelector("form")!.dispatchEvent(new dom.Event("submit", { bubbles: true, cancelable: true }) as unknown as Event));
     expect((await f.json("/habits")).habits[0].name).toBe("Read a little");
     expect(container.querySelector("form")).toBeNull();
-    expect(container.textContent).toContain("Read a little created.");
+    expect(container.textContent).not.toContain("Read a little created.");
     expect(container.querySelector(".ds-habit-chart")).not.toBeNull();
     await act(async () => buttonNamed("Sign out").click());
     expect(container.querySelector("#welcome-title")).not.toBeNull();
@@ -326,6 +326,39 @@ describe("homepage", () => {
     expect((await f.json("/today")).completed).toBe(2);
   });
 
+  test("a pending counter save leaves other habits usable and refreshes only its history", async () => {
+    const f = connectAccount();
+    const water = await f.json("/habits", "POST", { name: "Water", method: "count", target: 8, unit: "glasses" }, 201);
+    const reading = await f.json("/habits", "POST", { name: "Reading", method: "manual" }, 201);
+    await render("/");
+    const calendar = container.querySelector(`#history-${reading.id} .ds-calendar`);
+    const originalFetch = fetchMock.getMockImplementation()!;
+    let finish!: () => void;
+    const pending = new Promise<void>(resolve => { finish = resolve; });
+    fetchMock.mockImplementation(Object.assign(async (input: Parameters<typeof fetch>[0], init?: RequestInit) => {
+      if (init?.method === "PUT" && String(input).includes(`/habits/${water.id}/`)) await pending;
+      return originalFetch(input, init);
+    }, { preconnect: fetch.preconnect }));
+    fetchMock.mockClear();
+    await act(async () => buttonNamed("Increase Water").click());
+    expect(buttonNamed("Increase Water").disabled).toBe(true);
+    const check = container.querySelector<HTMLInputElement>('[aria-label="Reading done"]')!;
+    expect(check.disabled).toBe(false);
+    await act(async () => check.click());
+    expect(check.checked).toBe(true);
+    expect(buttonNamed("Increase Water").disabled).toBe(true);
+    expect((await f.json("/today")).completed).toBe(1);
+    fetchMock.mockClear();
+    await act(async () => { finish(); await pending; });
+    expect(buttonNamed("Increase Water").disabled).toBe(false);
+    expect(container.querySelector<HTMLInputElement>('[aria-label="Total Water"]')!.value).toBe("1");
+    expect(container.querySelector(`#history-${reading.id} .ds-calendar`)).toBe(calendar);
+    const historyRequests = fetchMock.mock.calls.map(([url]) => String(url)).filter(url => url.includes("/calendar?"));
+    expect(historyRequests).toHaveLength(1);
+    expect(historyRequests[0]).toContain(`/habits/${water.id}/calendar?`);
+    expect((await f.json("/today")).completed).toBe(1);
+  });
+
   test("inline habit edits persist configuration and delete archives without losing earlier history", async () => {
     const f = connectAccount();
     f.setTime("2026-09-03T12:00:00Z");