ci: free runner disk for add-on jobs and fix the Memory delete spec

The add-on jobs stop in prepare.sh when less than 20 GiB is free, and
the hosted runner image no longer leaves that much. Add a small script
that removes the unused preinstalled toolchains in parallel and prints
df before and after, and run it first in both jobs.

The Memory delete spec expected one status element. The page live
region and the toast container both carry role=status, so two match.
Check the page live region on its own and the toast as the second.

Assisted-by: Claude:claude-sonnet-5-5

.github/workflows/addons-tests.yml

@@ -83,6 +83,10 @@ jobs:
         uses: actions/checkout@v7
         with:
           persist-credentials: false
+      - name: Free disk space
+        # prepare.sh stops below 20 GiB free. The hosted runner image ships
+        # toolchains this job never uses; remove them before anything installs.
+        run: sh scripts/ci/free-runner-disk.sh
       - name: Setup Go
         uses: actions/setup-go@v6
         with:
@@ -149,6 +153,10 @@ jobs:
         uses: actions/checkout@v7
         with:
           persist-credentials: false
+      - name: Free disk space
+        # prepare.sh stops below 20 GiB free. The hosted runner image ships
+        # toolchains this job never uses; remove them before anything installs.
+        run: sh scripts/ci/free-runner-disk.sh
       - name: Setup Go
         uses: actions/setup-go@v6
         with: