Update GitHub Actions workflow to conditionally build mcpproxy binary for Windows and Unix-like systems

Author: Dumbris

.github/workflows/pr-build.yml

@@ -43,7 +43,11 @@ jobs:
         shell: bash
         run: |
           VERSION=pr-${{ github.event.number }}-${{ github.sha }}
-          go build -tags nogui -ldflags "-X main.version=${VERSION}" -o mcpproxy ./cmd/mcpproxy
+          if [[ "${{ runner.os }}" == "Windows" ]]; then
+            go build -tags nogui -ldflags "-X main.version=${VERSION}" -o mcpproxy.exe ./cmd/mcpproxy
+          else
+            go build -tags nogui -ldflags "-X main.version=${VERSION}" -o mcpproxy ./cmd/mcpproxy
+          fi
 
       - name: Test version output
         shell: bash