release: the Plasma classroom becomes stable 0.2.0

0.1.50 was taken to the church and the things a container cannot answer
were answered on the hardware: boot, autologin, the panel after a reboot,
panel and browser scaling, Wonder Ink, Parent Call opening in the corner
and reaching the sanctuary with a typed name, readable and silent
notifications, HDMI audio and the volume keys.

The promotion is a fast-forward. The experiment was cut from the
published stable source and never diverged from it, so master reaches
this work without a merge and there is one history.

One thing changed for the release. The channel rules turn around:
classroom-v2 and hyprland are the obsolete channels now and a room on
either comes home to stable, while canary — where the next development
release goes — and any channel somebody named by hand stay where they
were put. A fresh installation has always defaulted to stable.

Nothing else moved. This is the 0.1.50 that was verified, with a version
number and a channel rule.

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

tests/test-migration.sh

@@ -158,8 +158,12 @@ check(
     'OBSOLETE_KEYS = ("COMPOSITOR", "HYPR_APPEARANCE")' in migrate,
 )
 check(
-    "and comes off any channel that would undo the upgrade",
-    'OBSOLETE_CHANNELS = {"stable", "canary", "hyprland"}' in migrate,
+    "and comes off the channels that carried the experiment",
+    'OBSOLETE_CHANNELS = {"classroom-v2", "hyprland"}' in migrate,
+)
+check(
+    "onto the stable line, which the Plasma classroom now is",
+    'CHANNEL = "stable"' in migrate,
 )
 check(
     "the rest of device.conf is rewritten line by line, not regenerated",