test(cypress): Replace SortableJS 1/4: characterize column header reorder ahead of SortableJS removal

[6pac-ai]

Context

First of a planned series of PRs to drop the SortableJS dependency, porting slickgrid-universal's refactor(core)!: drop SortableJS dependency (#2634) to this repo. Header column reordering — the main SortableJS-dependent feature — has very little dedicated e2e coverage today, so this first PR lands characterization tests that pin the observable behavior. They pass against the current SortableJS implementation and must keep passing unchanged when the native drag engine replaces it in the follow-up PR.

No src/ changes — this PR only touches cypress/.

What's in here

• cypress/support/drag.ts — overwrites the drag command from @4tw/cypress-drag-drop with a native HTML5 DnD event sequence (pointerdown/mousedown → dragstart → dragenter/dragover → drop → dragend → pointerup/mouseup) sharing one DataTransfer and real coordinates. Ported from Slickgrid-Universal's version of the same helper, extended so a single command drives both SortableJS today and a native engine later:
  • prepends pointerdown/mousedown — SortableJS only arms itself from a press;
  • yields a macrotask after dragstart — SortableJS activates the drag on _nextTick;
  • dropSide option lands drops decisively past the target midpoint (75%/25%) so the before/after insertion intent is unambiguous regardless of which engine interprets it.
• cypress/e2e/example14-column-reorder.cy.ts — plain reorder in both directions; onColumnsReordered payload shape (impactedColumns, previousColumnOrder); no event when the order is unchanged; unorderable columns (cannot be dragged, cannot be dropped onto, can still be resized); plus an it.skip hidden-column test documenting a latent bug — the SortableJS toArray() read-back silently loses hidden columns on any reorder — to be enabled when the native engine (which fixes it) lands.
• cypress/e2e/example-frozen-columns-reorder.cy.ts — reorder within the frozen (left) and non-frozen (right) sections; the frozen boundary is uncrossable in both directions; horizontal scroll position preserved after reorder; edge auto-scroll starts during a drag past the grid edge and stops on drop.
• cypress/e2e/example-draggable-grouping-header-drop.cy.ts — cross-list header→dropzone drag (the SortableJS group: { pull: 'clone' } semantics that the SlickDraggableGrouping port must reproduce later).

Verification

• Full 47-spec Cypress suite: 599/601 passing, 0 failures (2 intentional pendings).
• The three existing specs that already dragged headers via .drag() (example-0032-row-span-many-columns, example-0070-plugin-state, example-grid-menu) pass unchanged through the overwritten command, as do both draggable-grouping pill-drag specs — i.e. the new command is proven against SortableJS on pre-existing expectations.

Next up: the native column reorder engine in slick.interactions.ts (branch refactor/drop-sortablejs, stacked on this one).

🤖 Generated with Claude Code

[6pac]

@ghiscoding this is 1 of 4 of the Remove SortableJS module. It just adds tests. Check it out and merge if you're happy.

[ghiscoding]

@6pac it seems ok since it seems to copy my own tests implementation. However I'd like to finish the variable row height and release that. Also just to remind you that dropping SortableJS probably shouldn't be merged into master, but rather into a different branch for future major version.

You can merge it seems ok, I'm going to bed soon

[ghiscoding]

ok just merging then, it seems ok