feat: let a teacher ask the sanctuary to call a child's parent

The coordinator already existed on the control computer and its contract
is frozen, so this is the classroom half of a contract that was read from
its README and source rather than guessed: four fields out, the status
topic subscribed before anything is published, and every word the teacher
reads taken from the coordinator's own message field.

It is a separate process, not a Plasma applet. A broker library, a
network timeout and a text entry have no business inside the only way a
teacher has of getting anywhere; if this dies the bar is untouched.

The panel mark is Breeze's call-outgoing. The old one was a bell, sitting
two inches from Plasma's notification bell in the same bar and meaning
something entirely different.

Two things it will not do: claim a call was displayed, and let a teacher
type the room. The machine already knows which room it is.

Sixty tests cover the contract without a broker. The live path was proven
against the real coordinator running in the lab, on a loopback broker,
with ProPresenter mocked and the church's networks rejected from inside
the container first.

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

config/plasma/applications/ekklesia-parent-call.desktop

@@ -1,10 +1,22 @@
 [Desktop Entry]
 Type=Application
 Name=Parent Call
-Comment=Ask for a child's parent to come to the room
+Comment=Ask the sanctuary to call a child's parent to this room
+# Breeze's own, and deliberately not a bell.
+#
+# The previous mark was a bell, which sat two inches from Plasma's
+# notification bell in the same bar and meant something entirely
+# different. A handset with an outgoing arrow cannot be mistaken for an
+# alert: it reads as placing a call, and the arrow says the call leaves
+# this room. No stock Breeze icon combines a person with a call, so the
+# unambiguous half was chosen over the half that could be read as user
+# settings — which is what two grey people on a panel look like.
+Icon=call-outgoing
 Exec=/usr/local/bin/classroom-parent-call
-Icon=ekklesia-parent-call
 Terminal=false
 Categories=Utility;
-StartupNotify=false
-NoDisplay=false
+StartupNotify=true
+StartupWMClass=classroom-parent-call
+# Never in an application list. It is reached from the bar, and it is not
+# one of the room's applications.
+NoDisplay=true