ci/docs: drop current branch references after rename to rolling

Cleanup PR following the current→rolling default-branch rename. Drops
the now-stale current branch from workflow triggers, flips remaining
defaults, and updates documentation/templates.

Workflows:
- pr-mirror-repo-sync.yml: branches narrowed to [rolling]; workflow_dispatch
  default and choice list now rolling-only; sync_branch fallback flipped
  from 'current' to 'rolling'.
- check-open-prs-conflict.yml: dropped current from push.branches.
- update-version-tags.yml: dropped current from push.branches and from
  the case statement (now bare 'rolling) TAG=rolling').
- submodules.yml: renamed update_current job, branch
  update-dependencies-current, and the related commit/title strings to
  rolling.
- update-translations.yml: PR branch update-translations-current renamed
  to update-translations-rolling.
- ai-validation.yml: prompt example updated.

Docs/templates:
- docs/conf.py: READTHEDOCS_GIT_IDENTIFIER fallback flipped to 'rolling';
  comment block updated to describe the rolling branch (the user-facing
  "(current)" suffix is release-channel terminology and remains).
- README.md: branching-scheme section now describes rolling as the
  default branch, with a note about the rename date.
- .github/PULL_REQUEST_TEMPLATE.md: CONTRIBUTING link points at
  blob/rolling.

External @current refs to vyos/.github and vyos/vyos-cla-signatures are
left untouched — they reference those repos' default branches and are
unaffected by this repo's rename.

🤖 Generated by [robots](https://vyos.io)

1 files changed, 4 insertions, 4 deletions

diff --git a/.github/workflows/submodules.yml b/.github/workflows/submodules.yml
index 24b6c505..bb93b93f 100644
--- a/.github/workflows/submodules.yml
+++ b/.github/workflows/submodules.yml
@@ -5,7 +5,7 @@ on:
   # 06:00 UTC on Monday
     - cron:  '0 6 * * 1'
 jobs:
-  update_current:
+  update_rolling:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
@@ -31,12 +31,12 @@ jobs:
         uses: peter-evans/create-pull-request@v6
         with:
           token: ${{ secrets.PR_ACTION_DOCUMENTATION_SUBMODULE_UPDATE }}
-          commit-message: "Github: update current branch"
-          title: "Github: update current branch"
+          commit-message: "Github: update rolling branch"
+          title: "Github: update rolling branch"
           body: |
             Autoupdate vyos-1x submodule
             update releasenotes
-          branch: update-dependencies-current
+          branch: update-dependencies-rolling
           delete-branch: true
 
   update_sagitta: