fix(pi): reject broken managed tool binaries

third_party/pi/packages/coding-agent/src/utils/tools-manager.ts

@@ -72,8 +72,8 @@ const TOOLS: Record<string, ToolConfig> = {
 function commandExists(cmd: string): boolean {
 	try {
 		const result = spawnSync(cmd, ["--version"], { stdio: "pipe" });
-		// Check for ENOENT error (command not found)
-		return result.error === undefined || result.error === null;
+		// Downloaded generic Linux binaries can exist but fail on NixOS before they print a version.
+		return (result.error === undefined || result.error === null) && result.status === 0;
 	} catch {
 		return false;
 	}
@@ -86,7 +86,7 @@ export function getToolPath(tool: "fd" | "rg"): string | null {
 
 	// Check our tools directory first
 	const localPath = join(TOOLS_DIR, config.binaryName + (platform() === "win32" ? ".exe" : ""));
-	if (existsSync(localPath)) {
+	if (existsSync(localPath) && commandExists(localPath)) {
 		return localPath;
 	}