ci: use full git history for downstream workflow checkout

actions/checkout defaults to a shallow clone; pluggy installs as -e ../..
need a real tree (e.g. setuptools-scm). Set fetch-depth: 0.

Co-authored-by: Cursor AI <ai@cursor.sh>
Co-authored-by: Composer <composer@cursor.com>

Author: 3 people

.github/workflows/downstream.yml

@@ -41,6 +41,7 @@ jobs:
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
+          fetch-depth: 0
           persist-credentials: false
       - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
         with: