fix(pcexec): include stderr in error message for better debugging

plugin/tools/pcexec.ts

@@ -249,7 +249,7 @@ export async function pcexec(
           command: finalCommand,
         });
       } else {
-        const error = new Error(`Command failed: ${command}`) as PcExecError;
+        const error = new Error(`Command failed: ${command}\n${stderr}`) as PcExecError;
         error.code = code ?? undefined;
         error.signal = signal ?? undefined;
         error.stdout = sanitizedStdout;