feat: Wonder Ink looks like the classroom, and its preview shows the page

The tab strip is drawn from the classroom's own palette, the one the
panel, Parent Call and Presentations read: larger titles, an accent
under the active tab, worksheets marked with a document icon. Its one
corner widget is the lesson's size and Print — not a new-tab button. With
one tab the strip stays hidden, as before; a change of size shows a
moment's badge instead, and the right-click menu and keys still work.
The window is named "Lesson — Wonder Ink" and carries its own icon.

The print preview showed "Page 1 could not be shown" in the real
session while printing correctly: poppler 25.03 does not write to stdout
when asked for "-" — it writes a file called "-.png" into the current
directory, which for Wonder Ink is the teacher's home. Pages are now
rendered into a directory of their own, and the lab print check fails
any preview that does not draw its page.

The teacher's manual has lesson size and printing.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/manual/50-wonderink.md

@@ -20,10 +20,32 @@ 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.
 
+## Making the lesson bigger or smaller
+
+Press **Ctrl** and **+** to make the lesson bigger, **Ctrl** and **−** to
+make it smaller, and **Ctrl** and **0** to go back to normal. You can also
+right-click the lesson and choose **Make the lesson bigger**. When several
+tabs are open, the **− 100% +** buttons at the top right do the same.
+
+The size applies to every tab and is remembered next time.
+
+## Printing
+
+Press **Ctrl** and **P**, click **Print** at the top right, or right-click
+and choose **Print…**. You will see the pages exactly as they will print.
+
+* Choose **Only some pages** to print, for example, `2` or `1-3`.
+* Set **Copies** for the number of children.
+* Choose **Black and white** to save colour ink.
+
+Click **Print**. Wonder Ink says when the printer has it and goes back to
+the lesson. **Cancel** prints nothing.
+
 ## Worksheets and colouring pages
 
 Click the worksheet link in the lesson. It opens in a new tab, ready to
-read or print.
+read or print. A worksheet's own **−** and **+** at the top of the page
+make it bigger or smaller.
 
 Worksheets you download are kept separately from everything else on the
 computer, so they never get mixed up with anything.