Greptile Summary

This PR fixes a browser-side blank-screen crash (issue #48062) caused by src/infra/tmp-openclaw-dir.ts reading fs.constants.W_OK | fs.constants.X_OK at module scope, which would fail when node:fs is externalized in the browser bundle. The fix wraps that evaluation in a lazy getTmpDirAccessMode() helper that is only invoked inside resolvePreferredOpenClawTmpDir() — a function that runs exclusively in Node.js — so the browser bundle can import the module without crashing.

• Change is minimal and targeted: only the evaluation timing of two fs.constants accesses changes; all runtime behavior in Node.js remains identical.
• No logic regressions: both accessSync(...) call sites receive the same bitmask (W_OK | X_OK) as before.
• No issues found: the helper is unexported, called only within the function, and fs.constants values are stable integer literals so repeated calls are inconsequential.

Confidence Score: 5/5

• This PR is safe to merge — it is a one-file, surgical fix with no logic changes and a clear, well-described root cause.
• The diff is small (4 lines added, 1 removed) and changes only evaluation timing, not runtime behavior. The fix correctly defers fs.constants access to call time, which is the minimal correct solution for the reported import-time crash in the browser bundle. No new control flow, no new exports, and no impact on the Node.js code path.
• No files require special attention.

_{Last reviewed commit: 3a54b1a}

merged in 412811e, author credited in changelog.