ci: pin garble@v0.15.0 (v0.16.0 requires Go 1.26+)

Author: John Doe

.github/workflows/release.yml

@@ -56,7 +56,7 @@ jobs:
           (cd ../gust-x && go mod download)
 
       - name: Install garble
-        run: go install mvdan.cc/garble@latest
+        run: go install mvdan.cc/garble@v0.15.0
 
       - name: Build targets
         shell: bash