test(scripts): wait for the e2e state path file to have content (#128403)

* test(scripts): wait for the e2e state path file to have content

waitForFile returned as soon as the path file existed. The child creates that
file and writes it in separate syscalls, so the reader could observe it empty,
read "" as the state dir, and fail the existence assertion on a path that was
never written. That surfaces as "expected false to be true" under CI load.

Wait for non-empty content instead.

* test(scripts): make the state path publication race deterministic

The suite previously published the path in one write, so it passed with either
readiness predicate and protected nothing. Publish the empty file first and
delay the real write, which is the window a real writer leaves open, so the
case fails on the existence-only check and passes on the content-aware one.

* test(scripts): publish e2e state paths atomically

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

test/scripts/e2e-temp-state-dir.test.ts

@@ -98,14 +98,16 @@ describe("E2E temp state dirs", () => {
       const helperUrl = pathToFileURL(path.resolve("scripts/e2e/lib/temp-state-dir.ts")).href;
       writeFileSync(
         scriptPath,
-        `import { writeFileSync } from "node:fs";
+        `import { renameSync, writeFileSync } from "node:fs";
 import { createE2eStateDir } from ${JSON.stringify(helperUrl)};
 
 const state = await createE2eStateDir("openclaw-e2e-temp-state-signal-", {
   OPENCLAW_STATE_DIR: "",
 });
 state.registerExitCleanup();
-writeFileSync(${JSON.stringify(statePathFile)}, state.stateDir);
+// Publish atomically so the polling parent cannot observe an empty state-path file.
+writeFileSync(${JSON.stringify(`${statePathFile}.tmp`)}, state.stateDir);
+renameSync(${JSON.stringify(`${statePathFile}.tmp`)}, ${JSON.stringify(statePathFile)});
 setInterval(() => {}, 1000);
 `,
       );