feat: redesign v2 — inspector layout fix, editor scroll, diff moved to breadcrumb bar

- Fix editor scroll (min-height: 0 + overflow)
- Properties panel extends full height
- Moved Diff button to git-branch icon in breadcrumb bar
- Minor CSS fixes for app layout

src/App.css

@@ -37,6 +37,8 @@
 .app__editor {
   flex: 1;
   min-width: 0;
+  min-height: 0;
+  overflow: hidden;
   display: flex;
   flex-direction: column;
 }