Channel maintenance moves to the RoboStack monorepo

The staging copy (scripts/copy-to-distro-specific-channel.py and the hourly
copy-staging-packages workflow) now lives in RoboStack/robostack#97,
together with the prefix.dev -> anaconda.org mirror. With it go its tests (the last
ones here: pytest, the test task and its CI step) and anaconda-client.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: Tobias-Fischer

.github/workflows/checks.yml

@@ -15,7 +15,6 @@ jobs:
           persist-credentials: false
       - uses: prefix-dev/setup-pixi@9dabb60412d3d2d967a8d682f7ce01317af40514 # v0.11.0
       - run: pixi run lint
-      - run: pixi run test
       - run: pixi run build-docs
 
   dependabot: