fix: dont crash after reverting move

[maribethb]

The basics

• I validated my changes

The details

Resolves

Fixes
With two connected blocks on the workspace, move one to a different connection and commit the move.
Start moving the same block again, but hit escape before committing.
block_svg.ts:313 Uncaught HierarchyRequestError: Failed to execute 'appendChild' on 'Node': The new child element contains the parent.
at BlockSvg.setParent (block_svg.ts:313:44)3. Hit escape again
Keyboard shortcut named "commitMove" not found.
(anonymous) @ shortcut_registry.ts:80
dom.ts:119 Uncaught RangeError: Maximum call stack size exceeded
at dom.ts:119:24

Proposed Changes

• cleans up after a reverted keyboard move
• removes redundant cleanup code from revertDrag since it's handled in endDrag

Reason for Changes

Test Coverage

added test for this

Documentation

Additional Information

[microbit-robert]

This has one negative side-effect. Start a move on a top-level block, then cancel it with Esc. The block gets a fixed yellow (slightly muted?) outline and then you can no longer drag it with the mouse.

You can fix this by using the keyboard to start and confirm another move.