perf(test): optimize heavy suites and stabilize lock timing

src/infra/tailscale.ts

@@ -150,6 +150,11 @@ export async function getTailnetHostname(exec: typeof runExec = runExec, detecte
 let cachedTailscaleBinary: string | null = null;
 
 export async function getTailscaleBinary(): Promise<string> {
+  const forcedBinary = process.env.OPENCLAW_TEST_TAILSCALE_BINARY?.trim();
+  if (forcedBinary) {
+    cachedTailscaleBinary = forcedBinary;
+    return forcedBinary;
+  }
   if (cachedTailscaleBinary) {
     return cachedTailscaleBinary;
   }