fix: coordinate mobile workbench overlays

Independent fixed offsets caused the timeline, map dock, tool panel, and zoom controls to overlap. Derive them from one layout function and scope collapse to the expanded timeline state.

tests/browser/button-system.e2e.ts

@@ -113,6 +113,65 @@ test("mobile launchers and map dock keep non-overlapping touch targets", async (
   expect(rectangles[1]!.x + rectangles[1]!.width).toBeLessThan(rectangles[2]!.x);
 });
 
+test("mobile timeline only offers collapse after opening its detail sheet", async ({ page }) => {
+  await page.setViewportSize({ width: 375, height: 812 });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const timelineSummary = page.getByRole("region", { name: "移动端运行时间轴摘要" });
+  await expect(timelineSummary).toBeVisible();
+  await expect(timelineSummary.getByRole("button", { name: "隐藏运行时间轴" })).toHaveCount(0);
+  await timelineSummary.getByRole("button", { name: "打开完整运行时间轴" }).click();
+
+  const timelineSheet = page.getByRole("region", { name: "运行时间轴抽屉" });
+  await expect(timelineSheet).toBeVisible();
+  await timelineSheet.getByRole("button", { name: "收起时间轴" }).click();
+  await expect(timelineSheet).toBeHidden();
+  await expect(timelineSummary).toBeVisible();
+});
+
+test("mobile map tool panel stays above the bottom dock", async ({ page }) => {
+  await page.setViewportSize({ width: 375, height: 812 });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  await page.getByRole("button", { name: "更多：更多地图操作" }).click();
+
+  const toolPanel = page.getByRole("region", { name: "更多" });
+  const mapDock = page.locator('nav[aria-label="地图工具"]:visible');
+  await expect(toolPanel).toBeVisible();
+  await expect
+    .poll(async () => {
+      const [panelBox, dockBox] = await Promise.all([
+        toolPanel.boundingBox(),
+        mapDock.boundingBox()
+      ]);
+      if (!panelBox || !dockBox) return Number.POSITIVE_INFINITY;
+      return Math.round(panelBox.y + panelBox.height - dockBox.y);
+    })
+    .toBeLessThanOrEqual(-8);
+});
+
+test("mobile map zoom stays above the bottom dock", async ({ page }) => {
+  await page.setViewportSize({ width: 375, height: 812 });
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const mapZoom = page.getByRole("group", { name: "地图缩放" });
+  const mapDock = page.locator('nav[aria-label="地图工具"]:visible');
+  await expect(mapZoom).toBeVisible();
+  await expect
+    .poll(async () => {
+      const [zoomBox, dockBox] = await Promise.all([
+        mapZoom.boundingBox(),
+        mapDock.boundingBox()
+      ]);
+      if (!zoomBox || !dockBox) return Number.POSITIVE_INFINITY;
+      return Math.round(zoomBox.y + zoomBox.height - dockBox.y);
+    })
+    .toBeLessThanOrEqual(-8);
+
+  const zoomBox = await mapZoom.boundingBox();
+  expect(Math.round(375 - zoomBox!.x - zoomBox!.width)).toBe(12);
+});
+
 test("Agent content buttons do not gain a border while pressed", async ({ page }) => {
   await page.setViewportSize({ width: 1440, height: 900 });
   await page.goto("/", { waitUntil: "domcontentloaded" });