fix(FN-1606): constrain task detail dropdown menus to viewport on mobile

- Add mobile CSS rules for .detail-actions-menu and .detail-move-menu dropdowns
- Position dropdowns above action bar with bottom: calc(100% + 4px)
- Constrain max-height to calc(100dvh - 120px) for viewport fit
- Enable overflow scrolling with -webkit-overflow-scrolling: touch
- Fix test assertion to match multi-selector CSS format

packages/dashboard/app/components/__tests__/core-modals-mobile.test.tsx

@@ -101,4 +101,23 @@ describe("core modals mobile css coverage", () => {
     expect(mobileBlock).toContain(".gm-nav-item {");
     expect(mobileBlock).toContain("min-height: 36px;");
   });
+
+  it("TaskDetailModal: action dropdown menus have max-height constraint on mobile", () => {
+    const css = fs.readFileSync(stylesPath, "utf-8");
+    const mobileBlock = getMainMobileBlock(css);
+
+    // Verify dropdown menu selectors are in mobile block (selectors share the same line)
+    expect(mobileBlock).toContain(".detail-actions-menu,");
+    expect(mobileBlock).toContain(".detail-move-menu {");
+
+    // Extract the dropdown menu rule block and verify constraints
+    const menuBlockMatch = mobileBlock.match(
+      /\.detail-actions-menu,\s*\.detail-move-menu\s*\{[^}]+\}/s,
+    );
+    expect(menuBlockMatch).not.toBeNull();
+    const menuBlock = menuBlockMatch![0];
+
+    expect(menuBlock).toContain("max-height");
+    expect(menuBlock).toContain("overflow-y: auto");
+  });
 });

packages/dashboard/app/styles.css

@@ -6560,10 +6560,13 @@ body {
     min-width: 0;
   }
 
-  /* Mobile dropdown menus — position above action bar */
+  /* Mobile dropdown menus — position above action bar, constrained to viewport */
   .detail-actions-menu,
   .detail-move-menu {
     bottom: calc(100% + 4px);
+    max-height: calc(100dvh - 120px);
+    overflow-y: auto;
+    -webkit-overflow-scrolling: touch;
   }
 
   .modal-header {