fix: always set windowsHide on Windows for stdio transport

Set windowsHide to true for all Windows apps, not just Electron.
Non-Electron apps (e.g., VS Code extensions, CLI tools) also show
an empty cmd.exe console window when spawning MCP servers via stdio.

Remove the now-unused isElectron() helper.

Fixes #1638

Author: Charlie Tonneslan

packages/client/src/client/stdio.ts

@@ -126,7 +126,7 @@ export class StdioClientTransport implements Transport {
                 },
                 stdio: ['pipe', 'pipe', this._serverParams.stderr ?? 'inherit'],
                 shell: false,
-                windowsHide: process.platform === 'win32' && isElectron(),
+                windowsHide: process.platform === 'win32',
                 cwd: this._serverParams.cwd
             });
 
@@ -258,7 +258,3 @@ export class StdioClientTransport implements Transport {
         });
     }
 }
-
-function isElectron() {
-    return 'type' in process;
-}