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/host.md

@@ -4,17 +4,32 @@ The host starts a session, invites the guests and drives the session:
 puts images on the page, starts new pages, loads pages from a notebook,
 and decides which guests may do the same.  In a lesson, the teacher is
 the host.  Everything in [A guest's Kokkoja](guest.md) applies to the host
-too; this part describes what is added, and how to install the Kokkoja
-program, which a host needs.
+too; this part describes what is added.
+
+## Hosting from the web site, or with the Kokkoja program
+
+A host, like a guest, can use Kokkoja with nothing installed: open
+`https://kokkoja.andykopra.com/` in a browser, enter a name, press
+**Start a session**, and the invitation is ready in the Session window.
+Your notebooks are then kept inside that browser, as a guest's are (see
+"Your notebook" in the guest's part): they belong to that browser on
+that computer, and a page leaves it by **Keep** or **Export**, which
+download it.  "Image" asks for the file with the browser's own chooser.
+
+If you would rather have your notebooks as ordinary directories of
+files, where you can open, copy, back up and send them, run the Kokkoja
+program on your own computer.  It is a small Python program with two
+jobs: it shows Kokkoja in your web browser, and it reads and writes
+your notebooks as directories and files.  It listens only to your own
+computer and talks to nothing else but the relay you name.  Your
+identity, too, then belongs to your computer rather than to one
+browser, so your writing from an earlier lesson is yours from any
+browser there.  A teacher who keeps notebooks of exercises and a
+notebook per student will want the program; for a first session the
+web site is enough.
 
 ## Installing the Kokkoja program
 
-A guest can join from a web site with nothing installed.  A host runs the
-Kokkoja program on their own computer.  It is a small Python program with
-two jobs: it shows Kokkoja in your web browser, and it reads and writes
-your notebooks as ordinary directories and files.  It listens only to
-your own computer and talks to nothing else but the relay you name.
-
 You need:
 
 * **Linux or macOS.**  Windows has not been tried yet.
@@ -97,6 +112,8 @@ Other options, all optional:
   yourself.
 * `--site ADDRESS` names the web site that invitations link to.  You
   need it only if your server's web site is not at the relay's host.
+* `--trash DIRECTORY` is where deleted notebooks and pages are moved,
+  instead of your system's Trash; `--trash none` deletes them outright.
 
 ## Starting a session
 
@@ -217,7 +234,7 @@ just large enough for everything on it, images and writing, with the
 margin of 5 mm around, which trims a page down to its exercise before you keep
 or export it.  A blank page cannot shrink.
 
-**Notebook** starts a new page for everyone from a page kept in one of
+**Notebooks** starts a new page for everyone from a page kept in one of
 your notebooks, with everything that was written on it.  A chooser shows
 your notebooks on the left and small pictures of the chosen notebook's
 kept pages on the right.  The loaded page is a copy: the kept page is
@@ -226,9 +243,23 @@ belongs to the participant who wrote it, so a student's answers from an
 earlier lesson are still theirs, and your corrections still yours.
 
 This is also how you return to an earlier page of the session: the page
-was kept when you left it, and **Notebook** brings it back as a new page.
+was kept when you left it, and **Notebooks** brings it back as a new page.
 A lesson might go: **New**, **Image** for the exercise, work, **New**
-for a point of grammar, work, **Notebook** to return to the exercise.
+for a point of grammar, work, **Notebooks** to return to the exercise.
+
+The same chooser deletes.  Every page card and every notebook in the
+list carries a small × mark; a tap marks it, a second tap unmarks it,
+and a marked notebook goes with every page in it.  As soon as something
+is marked, a **Delete** button in the chooser's header says how much:
+"Delete 3 pages?", "Delete 1 notebook and 3 pages?".  The first press
+says what will happen, "Press again to move 3 pages to the Trash";
+the second does it.  With the Kokkoja program, deleted notebooks and
+pages are moved to your system's Trash, where the
+file manager can put them back; the program's `--trash` option
+names another directory, or `none` to delete outright.  In the browser
+there is no Trash, and the button says "for good".  The notebook
+you are writing in cannot be deleted while you are: choose another
+notebook in the toolbar first.
 
 ## Co-hosts
 
@@ -257,7 +288,9 @@ The page you are on is written continuously to `Current.svg` in the
 current notebook, and copied to a dated file whenever the session moves
 on.  **Keep** makes such a copy now, named for the day and a serial
 number, such as `2026_10_06_02.svg`; pressing it again before anything
-has changed makes no second copy.  Any mark counts as a change, even a
+has changed makes no second copy, and neither does moving on from a
+page that is already kept, such as one loaded from the notebook and left
+as it was.  Any mark counts as a change, even a
 dot from a stray touch of the pen.  Use it to mark a state worth keeping
 on its own, or to add a finished page to a notebook of exercises.