fix(ci): add retention policy to release build artifacts (#585)

The upload-artifact step in the release workflow had no retention-days
set, causing intermediate build artifacts to persist at the repository
default of 90 days and consuming storage unnecessarily.

Add retention-days: 7 since these are intermediate artifacts consumed
by the publish job in the same workflow run — they do not need
long-term retention.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/workflows/release.yml

@@ -71,6 +71,7 @@ jobs:
               with:
                   name: zeroclaw-${{ matrix.target }}
                   path: zeroclaw-${{ matrix.target }}.*
+                  retention-days: 7
 
     publish:
         name: Publish Release