* core: add an optional pane name

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* server: add pane.rename and accept pane names as ids

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* cli: add pane rename

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* docs: specify pane names

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* server: resolve pane names for handlers that read the raw request

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* server: resolve pane names in tab.set_layout leaves

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* docs: note names in layout leaves

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Lucenx9 <185146821+Lucenx9@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>