Revert "Editor commands API / effects" (#1783)

Reverts tldraw/tldraw#1778.

Fuzz testing picked up errors related to deleting pages and undo/redo
which may doom this PR.

### Change Type

- [x] `major` — Breaking change

packages/editor/src/lib/hooks/useCanvasEvents.ts

@@ -84,14 +84,12 @@ export function useCanvasEvents() {
 
 				const files = Array.from(e.dataTransfer.files)
 
-				// the drop point should be offset by the position of the editor's container
 				const rect = editor.getContainer().getBoundingClientRect()
-				const point = editor.screenToPage({ x: e.clientX - rect.x, y: e.clientY - rect.y })
 
 				await editor.putExternalContent({
 					type: 'files',
 					files,
-					point,
+					point: editor.screenToPage(e.clientX - rect.x, e.clientY - rect.y),
 					ignoreParent: false,
 				})
 			}