fix: put the popup close button in the dock, and clear the printer location

Three things, none of them redesigns.

The close affordance for a secondary Chrome window was a separate
layer-shell surface anchored to that window's corner, repositioned by a
five-per-second poll. Any position change tore the surface down and
built another, so on real hardware it chased the window and flickered.
Removed entirely: the GTK button process, the geometry maths that placed
it, the --close-button mode that spawned it, and the poll loop that
drove it. The window helper no longer imports GTK at all.

The behaviour underneath it was right and is kept. The first Chrome
top-level is the classroom browser, tiled and borderless; later ones
float centred at about three quarters of the output. Creation order is
the only thing that can tell them apart — confirmed on a real session,
where every Chrome top-level shares app_id, shell, PID and a null
transient_for, and sway exposes no window properties for Wayland
toplevels at all. Titles are still not used. It now follows sway's own
window events instead of polling, so dragging a popup costs nothing.

Close moved into the dock, which was already on screen and does not
move, so it cannot chase anything. It appears only while a secondary
window is focused and runs kill on that one container. The helper
publishes which window that is; the dock watches the file rather than
polling. A stock sway title bar has no close button, so restoring the
border would not have solved this either.

Two bugs found by looking rather than by testing state. Chrome
renegotiates the size of a popup opened with explicit dimensions after
the resize returns, which left windows centred for a width they no
longer had; placement now settles and repeats once, at creation only, so
dragging is still free. And the dock's Close button came up empty
because show_all does not recurse into a no-show-all widget.

The printer's Location is now blank. CUPS prints it under the queue name
in every dialog, so "Ekklesia Classroom" was a second line the teacher
had to read past; the identity is one word. The already-configured check
includes Location, so a machine set up before this is corrected rather
than left as close enough.

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

docs/browser.md

@@ -41,6 +41,30 @@ None of this touches website logins. Wonder Ink, Google and YouTube
 sign-ins are ordinary site sessions and are unaffected by
 `BrowserSignin: 0`, which governs signing in to the *browser*.
 
+## Secondary Chrome windows
+
+Chrome gives the main browser and additional top-level windows the same
+`google-chrome` app ID, the same browser PID, and no reliable distinguishing
+properties. Page titles are site content and are deliberately not used.
+
+`classroom-chrome-windows` follows the Sway tree during the session and assigns
+roles by creation order:
+
+- the first Chrome top-level is the main classroom browser and remains tiled,
+  maximised and borderless;
+- every later Chrome top-level floats at 76% of the logical workspace, centred
+  above the main browser;
+- a red **Close ×** button is placed at its top-right and kills only that
+  secondary container;
+- when the secondary closes, the still-tiled main browser underneath has not
+  been moved or resized.
+
+The Sway `for_window` rule still only removes Chrome borders. There is no broad
+Chrome floating rule: the session helper issues commands against the exact
+`con_id` of each additional container. If the main window is closed first, the
+oldest remaining Chrome window is promoted back to the tiled, borderless main
+role.
+
 ## What the policies do not remove
 
 The avatar button stays in the toolbar. Verified by screenshotting
@@ -97,3 +121,51 @@ These two requirements genuinely conflict, and which one applies depends
 on how teachers actually sign in. Worth knowing before Sunday. If
 teachers use Wonder Ink email-and-password accounts, there is no
 conflict at all.
+
+
+## Extra browser windows
+
+The first Chrome top-level window is the classroom browser: tiled,
+borderless, filling the desktop above the dock. Every later Chrome
+top-level floats instead — centred, about three quarters of the output,
+borderless — so it sits over the browser rather than tiling beside it
+and shoving the lesson to half width.
+
+Which window is which can only be creation order. Verified on a real
+session: every Chrome top-level has the same `app_id`, the same
+`shell=xdg_shell`, the same PID, a null `transient_for`, and sway
+exposes no `window_properties`, `window_role` or `window_type` for
+Wayland toplevels at all. Page titles are deliberately not used.
+
+`classroom-chrome-windows` follows sway's own window events rather than
+polling, so dragging a popup costs nothing.
+
+### Closing one
+
+The Close button is **in the dock**, and only while a secondary window
+is focused. Clicking it runs `[con_id=N] kill` on that exact container:
+never the main browser, never a Chrome process.
+
+An earlier attempt anchored a close button to the popup's own corner as
+a separate layer-shell surface. On real hardware it chased the window
+and flickered, because every position change meant tearing a surface
+down and building another. The dock does not move, so it cannot chase
+anything.
+
+Note that a stock sway title bar has no close button, so putting the
+border back would not have solved closing either.
+
+### Printing
+
+A site's own Print button opens a Chrome window to render the document
+and then a print dialog on top of it. Verified in a real session: that
+is **three** top-level windows — the browser, the render window, and a
+separate `"Print"` dialog — and the render window is
+indistinguishable from a genuine popup by anything except its title.
+
+No special case was added, because there is no signal to special-case
+on. The generic treatment already produces the right result: the render
+window and the print dialog both float centred and borderless over an
+untouched main browser, the dialog is the obvious foreground window, and
+anything left behind is one dock click away. The render window used to
+be the one thing on screen wearing a sway title bar; it no longer is.