Add empty project creation, right-click context menus, and run-state tracking to Snippet Editor

[hatdragon]

• Add "New empty project" option to the "+ New" button dropdown menu with a name prompt dialog
• Add right-click context menus on sidebar rows for deleting projects/snippets and adding files to empty projects
• Track which projects have been run via ranProjects set, supporting multiple concurrent runs
• Show amber warning banner in editor when viewing files in a previously-run project, with Reload UI button
• Add "Running" panel at bottom of snippet list sidebar showing all ran projects with Reload UI button
• Banner and panel persist across navigation and update dynamically