Various UI and accessibility issues in SketchPad

This isn't a complete list but some initial issues.

[ ] It's possible for Flutter and the embedded editor (web view) to be managing focus, duplicating my actions. One in UI and another in editor. Only one of these should be managing it.
[ ] The link buttons in the expansion menu seem to have two focus targets, perhaps the icon is one too? The row should just be one focus target.
[x] The "Run" button should visually indicate it can't be clicked when compiling (similar to live or empty console button)
[ ] The categorical text on menus, such as "Dart" and "Flutter" in the Samples menu has too low contrast with background
[ ] The white dividers between entries in the package listing on light theme don't fit in
[ ] The console font should be fixed-width.
[ ] The console divider can't be expanded
[ ] The key bindings icon has a different color and hover style than the other icons (theme/menu)
[ ] The divider between sections of the Samples and extra dropdown menus is barely visible in Dark mode.
[ ] The dark theme codemirror view has a different background color than its padding (is this intentional?)
[ ] If you scroll down in the issues view (with 7+ issues), the top app bar changes colors.
[ ] The max amount of issues shown should have a lower limit with a shorter page.
[ ] Contrast of warning diagnostic icon on light theme is bad

dart-lang / dart-pad