Fullscreen overlay for distraction-free focus mode. Activated exclusively via bind:active — no built-in trigger.
Open Zen with an external trigger. Both Textarea instances share the same bind:value.
Zen works seamlessly with Textarea's adornment snippet and bind:this API.
Keep form values in the parent so closing and reopening the overlay preserves the draft.
The closeButton snippet receives a close callback. Disabling Escape and backdrop dismissal does not disable this explicit close control. Zen is independent of the modal/drawer manager stack and does not provide a focus trap.