change cell toolbar opacity on text overlap (#20)

Co-authored-by: Nicolas Brichet <32258950+brichet@users.noreply.github.com>

Author: Yahiewi

style/base.css

@@ -19,3 +19,17 @@
 #jupyter-ai-tutor-panel .jp-chat-input-container .jp-chat-input-toolbar {
   border-top: none;
 }
+
+/* Override toolbar visibility on cell overlap */
+/* stylelint-disable-next-line selector-class-pattern */
+.jp-toolbar-overlap .jp-cell-toolbar {
+  display: flex !important;
+  opacity: 0.15;
+}
+
+/* stylelint-disable-next-line selector-class-pattern */
+.jp-toolbar-overlap .jp-cell-toolbar:hover {
+  opacity: 1 !important;
+  background-color: var(--jp-layout-color1);
+  box-shadow: var(--jp-elevation-z2);
+}