Everyone has the same buttons; the view is personal

The host's rights and the co-host are gone: anyone in a session may
start a new page, put an image on the page, load a kept page, hide,
expand and shrink, and move or remove images and Hides; the page left
is kept in every notebook.  Fit and Normal scale act on your own screen
only.  A session goes on without whoever started it, and a newcomer to
an empty room starts page 1 with New.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

client/js/page_file.js

@@ -165,7 +165,7 @@ function strokeShapes(stroke) {
  * @param {object} options
  * @param {string} options.session  The session the page belongs to (its
  *     room id), so that returning to the session continues the page.
- * @param {string} options.hostId
+ * @param {string} options.hostId  Who started the session (`data-host`).
  * @param {Set<string>} [options.hidden]  Layers to leave out: for a picture
  *     of the page as someone shows it, never for the page file itself.
  * @returns {string}  The page file.