CI: install sshd from a fast mirror, or not at all

archive.ubuntu.com has been crawling (a few KB/s), taking the sshd install
in every job from 8 seconds to 3.5-9.5 minutes (another agent measured it;
the runner and inference-4090 were healthy). scripts/ci-sshd.sh skips the
install when the image has sshd, and otherwise points apt at
mirrors.edge.kernel.org first (both source layouts, 22.04 and 24.04).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

.gitea/workflows/ci.yml

@@ -39,12 +39,10 @@ jobs:
 
       - name: Install sshd
         # The tests reach "the build VM" over real SSH, through a throwaway
-        # sshd the test fixture starts (nisse_dev/testing.py).
-        run: |
-          SUDO=$(command -v sudo || true)
-          $SUDO apt-get update -qq
-          $SUDO apt-get install -y -qq openssh-server openssh-client > /dev/null
-          $SUDO mkdir -p /run/sshd
+        # sshd the test fixture starts (nisse_dev/testing.py). Skipped when the image has it; otherwise from
+        # a kernel.org mirror: archive.ubuntu.com has been slow enough to add
+        # minutes to every job.
+        run: scripts/ci-sshd.sh
 
       - name: Lint
         run: uv run ruff check .
@@ -100,12 +98,10 @@ jobs:
         run: uv sync --all-packages
 
       - name: Install sshd
-        # The build VM is a throwaway sshd here (scripts/e2e.sh --local).
-        run: |
-          SUDO=$(command -v sudo || true)
-          $SUDO apt-get update -qq
-          $SUDO apt-get install -y -qq openssh-server openssh-client > /dev/null
-          $SUDO mkdir -p /run/sshd
+        # The build VM is a throwaway sshd here (scripts/e2e.sh --local). Skipped when the image has it; otherwise from
+        # a kernel.org mirror: archive.ubuntu.com has been slow enough to add
+        # minutes to every job.
+        run: scripts/ci-sshd.sh
 
       - name: End-to-end tests
         env: