fix: allow text selection in calendar overlay without triggering drag

Added the `cancel` option to jQuery UI sortable configuration to
exclude overlay elements from initiating drag operations. This allows
users to select text within the calendar overlay (editorial metadata,
post details) without accidentally dragging the post to another date.

Fixes #27

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: GaryJones

CHANGELOG.md

@@ -8,6 +8,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 
 ### Fixed
 
+* fix: allow text selection in calendar overlay without triggering drag by @GaryJones in [#857](https://github.com/Automattic/Edit-Flow/pull/857)
 * fix: update post date to current time when publishing from custom status by @GaryJones in [#856](https://github.com/Automattic/Edit-Flow/pull/856)
 * fix: resolve calendar drag-and-drop not persisting post date changes by @GaryJones in [#854](https://github.com/Automattic/Edit-Flow/pull/854)
 * fix: guard against null return from get_edit_post_link() and get_permalink() by @GaryJones in [#853](https://github.com/Automattic/Edit-Flow/pull/853)

modules/calendar/lib/calendar.js

@@ -210,6 +210,7 @@ jQuery( document ).ready( function ( $ ) {
 		items: 'li.day-item.sortable',
 		connectWith: 'td.day-unit ul',
 		placeholder: 'ui-state-highlight',
+		cancel: '.item-overlay, .item-overlay *, .post-insert-overlay, .post-insert-overlay *',
 		start( event, ui ) {
 			$( this ).disableSelection();
 			edit_flow_calendar_close_overlays();