Codex-generated pull request

[cdreetz]

Codex generated this pull request, but encountered an unexpected error after generation. This is a placeholder PR message.

---

Codex Task

---

Note

Medium Risk
Touches session/sandbox setup and error classification, which can change how rollouts terminate and how failures are reported. Logic is straightforward but could alter behavior in edge cases where callers relied on raw exceptions or custom stop_errors defaults.

Overview
Improves error semantics for CUA mode. CUAMode.setup_state now wraps unexpected exceptions into new verifier error types (BrowserSessionSetupError for local HTTP setup and BrowserSandboxSetupError for sandbox setup), while rethrowing existing vf.Error unchanged.

Adjusts rollout stopping behavior. BrowserEnv now defaults stop_errors to include vf.SandboxError when mode="cua" (unless explicitly provided), and adds tests covering both the new exception wrapping and the default stop_errors behavior.

^{Written by Cursor Bugbot for commit da5366f. This will update automatically on new commits. Configure here.}