fix(snap): use basename for the artifact path so publish-edge finds it

Snap publish-edge failed with "'release/etherpad-desktop_0.2.0_amd64.snap'
is not a valid file" because actions/upload-artifact flattens path
patterns into the artifact root. The build job uploads `release/*.snap`,
which means the artifact's root contains the .snap file directly. When
publish-edge downloads the artifact, the file lands at the workspace
root — not under release/.

Output the BASENAME only from the find step, so the path is valid in
both the build context (where the file is at release/<name>.snap) and
the publish context (where it's at <name>.snap after download).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: JohnMcLear

.github/workflows/snap-publish.yml

@@ -70,9 +70,15 @@ jobs:
 
       - name: Locate snap file
         id: find
+        # Output the BASENAME, not release/<name>.snap. actions/upload-artifact
+        # flattens release/*.snap into the artifact root, so when publish-edge
+        # downloads it the file lands at the workspace root — `release/` doesn't
+        # exist there. Using just the basename keeps the same path valid in
+        # both the build job (after `cd release` is implicit) and the publish
+        # job (after artifact download).
         run: |
           file=$(ls release/*.snap | head -n1)
-          echo "path=$file" >> "$GITHUB_OUTPUT"
+          echo "path=$(basename "$file")" >> "$GITHUB_OUTPUT"
 
       - name: Upload snap artifact
         uses: actions/upload-artifact@v4