Respect put: false on the revert-to-origin path

[nandastone]

group.put: false is documented as preventing a sortable from receiving elements. It works correctly for cross-list drops from other sortables, but is silently ignored when a dragged item is reverted back to its own sortable.

This matters for clone-source lists (e.g. a sidebar with pull: 'clone', put: false, sort: false), items can be dragged out as clones, but nothing should be dropped back in. Currently, dragging an item out and then hovering back over the source triggers the revert branch, which bypasses checkPut entirely and reinserts dragEl into the source.

Sidebar                    Playlist

┌───────────┐              ┌───────────┐
│  Image    │              │  Scene 1  │
│  Video    │              │  Scene 2  │
│  Audio  │              │  Scene 3  │
└───────────┘              └───────────┘

1. Drag Image into Playlist (clone stays in Sidebar):

┌───────────┐              ┌───────────┐
│  Image    │              │  Scene 1  │
│  Video    │              │ [Image]   │
│  Audio  │              │  Scene 2  │
└───────────┘              │  Scene 3  │
                           └───────────┘

2. Hover cursor back over Sidebar:

┌───────────┐              ┌───────────┐
│ [Image]   │  <────────   │  Scene 1  │
│  Image    │   revert     │  Scene 2  │
│  Video    │   ignores    │  Scene 3  │
│  Audio  │   put:false  └───────────┘
└───────────┘
 ↑ dragEl forced back in,
   source now has both the
   clone AND the original

The non-owner branch of _onDragOver correctly gates on group.checkPut. The owner branch does not — it only checks canSort:

(isOwner
    ? canSort || (revert = parentEl !== rootEl)
    : putSortable === this || (checkPull(...) && group.checkPut(...))
)

The asymmetry means put: false is enforced everywhere except the one code path where the source sortable acts as its own drop target.

Proposed fix:

Add group.checkPut to the owner branch so the revert condition mirrors the non-owner branch:

? canSort || ((revert = parentEl !== rootEl) && group.checkPut(this, activeSortable, dragEl, evt))

This change only affects sortables that explicitly declare put: false. The default (put: true or unset) is unchanged because checkPut returns true.

[nandastone]

Unsure if I should add a new Testcafe fixture for this. Existing tests will catch any regressions. Please advise.