CI: runs on halogen's yukart registration of the flutter-android runner

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

docs/impl/plans/INITIAL.md

@@ -129,8 +129,13 @@ WiFi-only and does not help here. Untested in the car so far.
 
 ### CI
 
-`.gitea/workflows/ci.yaml` mirrors the android-stuff apps: host-mode runner on
-halogen, label `flutter-android`, analyze + test, then a debug APK artifact on
-push. The existing `halogen-android` runner is registered to the android-stuff
-org only, so this repo needs a runner registered to the `yukart` org (a second
-instance on halogen, the way `gitea-runner-audio` is set up) before jobs run.
+`.gitea/workflows/ci.yaml` mirrors the android-stuff apps: analyze + test, then a
+debug APK artifact on push, on label `flutter-android`.
+
+A Gitea repo has one owner and an org-scoped runner serves one org, so halogen
+carries two registrations of the same runner: `gitea-runner.service` for
+android-stuff and `gitea-runner-yukart.service` for this org. They share the
+`gitea-runner` user, HOME, Gradle/pub caches and the `/opt/flutter` +
+`/opt/android-sdk` toolchain — a second registration, not a second toolchain.
+`flutter-android-preflight` runs in every job, so drift after a `flutter upgrade`
+fails here before it fails on a build.