FileTree: List of valid files in error message is always empty

[mootari]

In https://svelte.dev/tutorial/svelte/universal-reactivity, when you add or rename a file with a name other than shared.svelte.js the following error message is displayed:

The missing file list in the message is sourced from workspace.exercise.editing_constraints which are commonly empty (only one tutorial defines them in its frontmatter).

The constraint is instead enforced via the file list in the solution store:

svelte.dev/apps/svelte.dev/src/routes/tutorial/[...slug]/filetree/Filetree.svelte

Lines 32 to 33 in 286e422

	add: async (name, type) => {
	const expected = $solution[name];

I suspect the right approach here might be to list only those entries that are present in solution but missing in workspace.files (and vice versa for rename and remove), to prevent the list from getting excessively long.