A host from the web site; the same page kept once; deleting from the Notebooks chooser

From the development repository at 299f73d, 2026-10-11:
hosting from the site documented; a page loaded from a notebook and left
unchanged is not kept again; notebooks and pages are deleted from the
chooser, to the system's Trash (--trash); the Notebooks button.

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

docs/implementation.md

@@ -26,8 +26,9 @@ Kokkoja is three programs and a few static files.
   session and nothing more: it cannot read them and it stores nothing.
   It is Python with one library, `websockets`.
 * **The web site** is the `client/` directory served over HTTPS, with a
-  `config.json` beside it, so that a guest can join without the local
-  program.  `deploy/` has the server setup.
+  `config.json` beside it, so that a guest can join, and a host can
+  start a session, without the local program.  `deploy/` has the server
+  setup.
 
 Every participant's computer holds the whole page.  Only changes travel:
 a stroke as it is drawn, a text block as it is typed, an erasure, a new
@@ -173,7 +174,14 @@ the user asks (**Keep**), and by the program whenever `Current.svg`
 is about to be given to another page: when the session moves to a new
 page, when the notebook is changed, and when a session begins and finds
 a page of another session in the notebook.  Nothing is copied if the
-page is blank or an identical copy already exists.
+page is blank or the same page is already kept in that notebook; a
+page loaded from a notebook and left unchanged is therefore not kept
+again, although the file names it as a new page.  A kept page or a
+whole notebook can be deleted from the Notebooks chooser; the local
+program moves it to the system's Trash (the freedesktop Trash on
+Linux, with the info file the file manager wants for putting it back;
+`~/.Trash` on macOS) unless `--trash` says otherwise, and the
+browser's notebook, having none, deletes for good.
 
 The file is an SVG document that any viewer displays: the images as
 embedded `<image>` elements, each layer as a group with the participant's