new: drag & drop primitive for Solid 2.0

.changeset/drag-new-package.md

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+---
+"@solid-primitives/drag-drop": minor
+---
+
+New package: `@solid-primitives/drag-drop` — composable drag-and-drop primitives for Solid 2.0.
+
+### Exports
+
+**Pointer-event DnD** (UI element dragging):
+- `makeDraggable` — non-reactive base, no Solid owner required
+- `makeDroppable` — non-reactive drop target base
+- `createDraggable` — reactive draggable with `isDragging`, `transform`, auto style/class; keyboard-accessible (`Space`/`Enter` to pick up/drop, arrow keys to nudge, `Escape` to cancel)
+- `createDroppable` — reactive drop target with `isOver`, `active`, auto style/class
+- `createSortable` — combines draggable + droppable on the same element
+- `createDragContext` — coordinates a tree of draggables and droppables, with optional `autoScroll` near viewport edges
+- `arrayMove` — pure reorder helper for `onDragEnd` + `createSortable`
+
+**Native HTML5 DnD** (file drops, `draggable="true"` elements):
+- `makeNativeDroppable` — non-reactive base with depth-counter fix for child elements
+- `createNativeDroppable` — reactive native drop zone for OS file drops
+
+**Collision detection strategies** (pure functions, pass to `createDragContext`):
+- `closestCenter`, `closestCorners`, `rectIntersection`, `pointerWithin` (default)
+
+### Notes
+
+- The reported `transform` is corrected for page scroll during a drag, so the dragged element doesn't visually drift from the pointer if the page scrolls mid-drag (needed for `autoScroll` to look right, and for any scrollable page in general).
+- `createDroppable`/`createSortable` log a dev-mode warning when used without a `createDragContext` ancestor, since `isOver`/`active` silently stay `false`/`null` in that case.
+- `isDragging`/`isOver` are backed by `createProjection` instead of a per-instance `active()?.id === id` memo, so a drag start/end or hover change in a large list only notifies the specific items involved.

packages/drag-drop/LICENSE

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+MIT License
+
+Copyright (c) 2026 Solid Primitives Working Group
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.