Sortable.js draggable must match direct children of .sortable-column.
Using .task-card (grandchild) caused Sortable to detach it from its
.task-card-zone wrapper, breaking HTMX OOB swap targets and making
drag appear to do nothing. Changed to .task-card-zone so the full
wrapper moves, keeping id= attributes intact for HTMX round-trips.
Also removed redundant form.dispatchEvent() before htmx.trigger()
which could cause a double submit on reorder.
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>