ci: remove main branch source guard

.github/workflows/guard-main-branch.yml

@@ -1,42 +0,0 @@
-name: Guard main branch
-
-on:
-  pull_request:
-    branches:
-      - main
-  merge_group:
-
-permissions: {}
-
-# DO NOT RENAME the job's `name:` — it is referenced by GitHub branch
-# protection as a required status check on `main`. Renaming silently
-# breaks the gate.
-jobs:
-  guard:
-    name: Verify PR source branch
-    runs-on: ubuntu-latest
-    timeout-minutes: 2
-    steps:
-      - name: Reject merge_group events
-        if: github.event_name == 'merge_group'
-        run: |
-          echo "::error::Merge queue is not supported for main. Disable merge queue or update this guard."
-          exit 1
-      - name: Check head branch name
-        env:
-          HEAD_REF: ${{ github.head_ref }}
-          HEAD_REPO: ${{ github.event.pull_request.head.repo.full_name }}
-          BASE_REPO: ${{ github.repository }}
-        run: |
-          echo "PR head repo: $HEAD_REPO"
-          echo "PR head branch: $HEAD_REF"
-          if [ "$HEAD_REPO" != "$BASE_REPO" ]; then
-            echo "::error::PRs to main must originate from the canonical repository ($BASE_REPO), not a fork ($HEAD_REPO). External contributors should open PRs against 'litellm_internal_staging' instead."
-            exit 1
-          fi
-          if [ "$HEAD_REF" = "litellm_internal_staging" ] || [[ "$HEAD_REF" == litellm_hotfix_?* ]]; then
-            echo "Allowed source branch."
-            exit 0
-          fi
-          echo "::error::PRs to main must originate from 'litellm_internal_staging' or a 'litellm_hotfix_*' branch. Got: '$HEAD_REF'. If this is a contribution, retarget the PR against 'litellm_internal_staging' instead."
-          exit 1