fix(release): use brews instead of homebrew_casks for CLI formula

homebrew_casks is for macOS .app bundles; brews is the correct
GoReleaser v2 key for CLI binaries. Also read Go version from go.mod
instead of hardcoding it.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/release.yml

@@ -20,7 +20,7 @@ jobs:
       - name: Setup Go
         uses: actions/setup-go@v5
         with:
-          go-version: "1.26"
+          go-version-file: server/go.mod
           cache-dependency-path: server/go.sum
 
       - name: Run GoReleaser