feat(FN-1137): improve mobile dropdown and file browser interactions

- Add viewport-aware positioning/clamping for Quick Scripts and Quick Entry dropdown menus
- Implement long-press context menu behavior in FileBrowser with iOS momentum scrolling support
- Expand dashboard CSS and component logic to stabilize mobile overlay behavior and remove unused inline WebKit style
- Add focused tests for FileBrowser, QuickScriptsDropdown, and mobile dropdown positioning plus README notes

packages/dashboard/app/styles.css

@@ -23450,3 +23450,58 @@ html .column.drag-over * {
   background: var(--border);
   margin: 8px 16px;
 }
+
+/* FN-1137: Quick scripts dropdown mobile viewport handling */
+@media (max-width: 768px) {
+  .quick-scripts-dropdown__menu {
+    max-height: min(60vh, 400px);
+    overflow-y: auto;
+    -webkit-overflow-scrolling: touch;
+  }
+}
+
+/* FN-1137: mobile dep dropdown overflow handling */
+@media (max-width: 768px) {
+  .dep-dropdown {
+    max-height: min(50vh, 240px);
+    overflow-y: auto;
+    -webkit-overflow-scrolling: touch;
+  }
+}
+
+/* FN-1137: file browser long-press and mobile context menu touch targets */
+.file-node {
+  touch-action: manipulation;
+}
+
+.file-node--long-pressing {
+  background: var(--card-hover);
+}
+
+@media (max-width: 768px) {
+  .file-browser-context-menu__item {
+    min-height: 44px;
+  }
+}
+
+/* FN-1137: iOS momentum scrolling conventions */
+.dep-dropdown,
+.model-combobox-list,
+.quick-scripts-dropdown__list,
+.file-browser-list {
+  -webkit-overflow-scrolling: touch;
+}
+
+@media (max-width: 768px) {
+  /* iOS momentum scrolling for all modal content areas */
+  .modal-content,
+  .modal-body,
+  .modal-scroll,
+  .task-detail-content,
+  .agent-log-content,
+  .file-browser-list,
+  .settings-content,
+  .activity-log-content {
+    -webkit-overflow-scrolling: touch;
+  }
+}