fix: a room that was set up, a card where its button is, and larger cards

Parent Call told rooms they had never been set up. Nothing about the
rooms was wrong. Read from the church broker: …/coordinator and
…/pending are retained and …/mode is absent, and the coordinator's own
source says why — it publishes the retained mode only in answer to an
operator writing to …/mode/set, and nobody ever has. Every classroom
waited a second and a half for a message that will never exist.

A missing mode is now read as the coordinator's own default rather than
as an unconfigured room: the room offers the call and lets the sanctuary
end answer, because that is the end that knows. A mode that really is
off still refuses, in the coordinator's words, and a broker that is
missing or unreachable still says which of those it is. Proved against a
rig broker made to match the church's exactly, with a call landing on
the sanctuary mock.

The card is anchored to the bottom-left corner instead of centred, by
layer shell, which is what the disc player's cover has used under KWin
for months. Anchoring rather than positioning is what makes it right at
1080p and at 4K without a coordinate anywhere. It falls back to the
centred card if the library is missing.

Notifications are sized for a room. Every Plasma measurement is a grid
unit and a grid unit is the height of the general font, so the font is
the lever — 15 point instead of Breeze's 10, which takes the card from
about 350x110 to about 410x145 at 100% and doubles again at 200%. Text,
icon, padding and buttons move together. The chime stays off. No shell
package: that path cost the panel and is not coming back.

And the product name is gone from everything a teacher sees. The
notification card is from Classroom, the disc player's from DVD.

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

docs/screenshots/README.md

@@ -101,6 +101,16 @@ container lab. See [../classroom-v2-experiment.md](../classroom-v2-experiment.md
 | `pc-unreachable`, `pc-not-configured` | Parent Call telling a broker it cannot reach from one that was never set up |
 | `dvd-absent-bar` | the bar on a machine with no optical drive |
 
+## A morning in the rooms
+
+| | |
+| --- | --- |
+| `pc-no-mode` | Parent Call ready against a broker with no retained mode — the state that used to say the room was never set up |
+| `pc-bottom-left`, `pc-200-package` | the card anchored bottom-left at 100% and at 200% |
+| `notif-package-100`, `notif-package-200` | the notification card at both scales, from `Classroom` |
+| `notif-13pt`, `notif-15pt` | the two font sizes that were weighed for it |
+| `pc-typed-layer` | the card gone: the lab's keyboard tool closes it, which is why typing is still a bench test |
+
 ## Failures, kept
 
 | | |