README: expand Limitations with an explicit Mobile/Android note

Sets expectations clearly: the plugin is desktop-only (custom code-block
rendering + webview messaging aren't reliably supported on mobile), but
the underlying to-dos sync and appear in Joplin's native mobile views.

README.md

@@ -87,10 +87,16 @@ Everything is clickable: single-event tiles, every row of a multi-event hover ca
 
 ## Limitations
 
-- Desktop only (relies on plugin messaging and the `openNote` command; mobile plugin support is partial).
+- **Desktop only.** See the note below.
 - `month-grid` always shows the current month; there is no month navigation yet.
 - The calendar refreshes when the note re-renders (e.g. switching notes); edits to *other* notes don't live-update an open calendar.
 
+### Mobile / Android
+
+This plugin is built for **Joplin desktop** and is not expected to work on the Android or iOS apps. It depends on rendering custom code blocks in the note viewer and on two-way messaging between that view and the plugin — capabilities Joplin's mobile apps have historically not supported, or supported only partially. On mobile, a `gtd-calendar` block will most likely render as plain text or not at all, and drilldown won't work. The companion *Repeating To-Dos* plugin is desktop-only as well.
+
+Your data is unaffected, though: the calendar is only a *view*. Your to-dos and their due dates are ordinary Joplin items that sync to mobile normally and appear in Joplin's built-in to-do list and search, with alarms intact — you just won't see the calendar rendering there. If you want a quick scheduled-items view on mobile, pair the calendar with Joplin's native to-do view or the *Embed Search* plugin on desktop.
+
 ## Bugs & feedback
 
 Issues and ideas: [the repository](https://gitea.skeletonworks.online/vwiebe/joplin-plugin-gtd-calendar/issues), or find me on the Joplin forum.