fix(charts): preserve comparison types and draggable window headings

Keep current lines and historical scatter points in a dedicated comparison chart type. Expose floating headings and use idempotent placement so StrictMode no longer masks production overlap.

tests/browser/investigation-chart-windows.e2e.ts

@@ -9,6 +9,50 @@ const chart = (index: number) => ({
 
 test.setTimeout(60_000);
 
+for (const height of [900, 720]) {
+  test(`multiple chart headings stay accessible and drag on first press at ${height}px height`, async ({ page }, testInfo) => {
+    await page.setViewportSize({ width: 1440, height });
+    const task = investigationFixture(1, "多图窗口拖动核查");
+    const mock = await mockInvestigationPresentation(page, [task]);
+    await selectInvestigation(page, task.title);
+    for (let index = 1; index <= 4; index++) {
+      await mock.emit(task, { ...chart(index), chart_id: `pressure-${index}` });
+      await expect(page.getByRole("dialog", { name: `合成压力分析 ${index}`, exact: true })).toBeVisible();
+    }
+    if (height === 900) await page.setViewportSize({ width: 1440, height: 720 });
+    for (let index = 1; index <= 4; index++) {
+      const popup = page.getByRole("dialog", { name: `合成压力分析 ${index}`, exact: true });
+      const heading = popup.locator(".floating-window-heading");
+      const box = (await heading.boundingBox())!;
+      expect((await popup.boundingBox())!.y).toBe(64 + (index - 1) * (box.height + 8));
+      const target = { x: box.x + box.width / 2, y: box.y + box.height / 2 };
+      expect(await page.evaluate(({ x, y }) => document.elementFromPoint(x, y)?.closest("[data-floating-window]")?.getAttribute("aria-labelledby"), target))
+        .toBe(await popup.getAttribute("aria-labelledby"));
+    }
+    await testInfo.attach(`multiple-charts-before-drag-${height}`, {
+      body: await page.screenshot({ path: testInfo.outputPath(`multiple-charts-before-drag-${height}.png`) }), contentType: "image/png"
+    });
+    for (const index of [1, 4, 2]) {
+      const popup = page.getByRole("dialog", { name: `合成压力分析 ${index}`, exact: true });
+      const before = (await popup.boundingBox())!;
+      const heading = (await popup.locator(".floating-window-heading").boundingBox())!;
+      const start = { x: heading.x + heading.width - 110, y: heading.y + heading.height / 2 };
+      await page.mouse.move(start.x, start.y);
+      await page.mouse.down();
+      await page.mouse.move(start.x - 120, start.y - 32, { steps: 12 });
+      await page.mouse.up();
+      await expect.poll(async () => Math.round((await popup.boundingBox())!.x - before.x)).toBe(-120);
+      await expect.poll(async () => Math.round((await popup.boundingBox())!.y - before.y)).toBe(-32);
+      expect((await popup.boundingBox())!.width).toBe(before.width);
+      expect((await popup.boundingBox())!.height).toBe(before.height);
+    }
+    await testInfo.attach(`multiple-charts-after-drag-${height}`, {
+      body: await page.screenshot({ path: testInfo.outputPath(`multiple-charts-after-drag-${height}.png`) }), contentType: "image/png"
+    });
+    expect(mock.mutations).toEqual([]);
+  });
+}
+
 test("live analysis opens a window, preserves its position and respects closing and task switches", async ({ page }, testInfo) => {
   const task = investigationFixture(1, "图表自动展示核查");
   const other = investigationFixture(2, "另一项调查");