docs: one manual, the pages a device has and a printable copy of all of them

Documentation becomes part of the release rather than a job afterwards.
docs/manual is now the only place teacher instructions are written, and
tools/build-manual produces both versions from it:

  classroom-manual.html   installed on every machine, showing only the
                          features THAT device has
  classroom-manual.pdf    the universal printed manual, every feature,
                          with a conditional sentence above each
                          optional page so it stays true in a room that
                          does not have them all

They cannot drift apart because neither is written by hand, and
build-release.sh builds and checks them on every release: a page that
declares a feature with no printed-if fails the build, because that is
exactly how the printed manual comes to state an optional feature as
though every room had it. So does a page naming a feature device.conf
does not have, and an optional feature with no page at all.

WHAT REACHES THE CLASSROOM ACCOUNT. Only a list of setting NAMES, and
only ones the package already defines as optional applications.
classroom-desktop-layout — already the one place that decides what a
device offers — writes them to /run/ekklesia-classroom/features.json,
and classroom-manual filters that against FEATURES before using it. No
values from device.conf, no broker password, no addresses. With no
manifest at all every page is shown, which is the printed manual and is
never wrong, only less specific.

Help is a Quick Launch button beside Parent Call, deliberately not in
the row with the applications: putting it there would move buttons
teachers reach for without looking. Every room gets it, because a
teacher who needs the manual is by definition one who does not know
where to look.

The PDF is written directly rather than converted. A manual is
headings, paragraphs, bullets, steps and one table; writing that with
the standard fonts is a couple of hundred lines and no dependency, so a
release can be built on any machine with Python. Pictures are embedded
in the digital manual as data URIs so it stays one file that works
wherever it is copied and with the network unplugged; the printed
manual names them instead, which is the one thing this builder does not
do and is noted where somebody would look for it.

Two defects found building it, both of which hung or corrupted the
output rather than failing: a paragraph opening with a bold word
matched the bullet guard but not the bullet rule, so nothing consumed
it and the build spun; and a list item wrapped across two source lines
ended the list, so a three-step procedure printed as three steps all
numbered 1.

Also adds the 0.2.6 physical checklist to docs/testing.md and the
release validator's checks for the Wi-Fi regression, the conversion
pipeline on a real Debian, the fonts, the manual and the dock order.

Co-Authored-By: Claude Opus 5 <[email protected]>

docs/manual/50-wonderink.md

@@ -0,0 +1,35 @@
+---
+title: Wonder Ink
+order: 50
+feature: WONDERINK_ENABLED
+printed-if: If Wonder Ink is available in your classroom
+---
+
+**Wonder Ink** opens the lesson. It is its own application, not the
+browser, and it opens straight into the lesson site.
+
+## Using it
+
+1. Click **Wonder Ink** on the bar.
+2. Sign in with your Wonder Ink account.
+
+A lesson often opens several tabs — the lesson, its video, an activity.
+They appear in a row across the top. Click a tab to move between them,
+and the **×** on a tab to close it.
+
+There is no address bar, on purpose. Wonder Ink can take you anywhere
+the lesson needs to go.
+
+## Worksheets and colouring pages
+
+Click the worksheet link in the lesson. It opens in a new tab, ready to
+read or print.
+
+Worksheets you download are kept separately from everything else on the
+computer, so they never get mixed up with anything.
+
+## When you have finished
+
+**Close Wonder Ink at the end of your session.** Closing it signs you
+out, so the next teacher in this room starts with their own account and
+not yours.