chore: import upstream snapshot with attribution

examples/sandbox/extensions/temporal/_worker_setup.py

@@ -0,0 +1,39 @@
+"""Worker startup diagnostics."""
+
+from __future__ import annotations
+
+YELLOW = "\033[1;33m"
+RESET = "\033[0m"
+
+
+def print_backend_warnings(registered_names: set[str]) -> None:
+    """Print a prominent warning banner for any unconfigured sandbox backends."""
+    import docker  # type: ignore[import-untyped]
+
+    backend_env = {
+        "daytona": "DAYTONA_API_KEY",
+        "e2b": "E2B_API_KEY",
+    }
+    missing = {name: var for name, var in backend_env.items() if name not in registered_names}
+    try:
+        docker.from_env().ping()
+    except Exception:
+        missing["docker"] = "Docker daemon"
+
+    if not missing:
+        return
+
+    lines = [
+        "WARNING: Some sandbox backends are NOT available.",
+        "Missing:",
+    ]
+    for name, var in sorted(missing.items()):
+        lines.append(f"  - {name} ({var})")
+    lines.append("The TUI will fail if you select an unconfigured backend.")
+    lines.append("To use them, set the missing env vars and restart the worker.")
+    width = max(len(line) for line in lines) + 4
+    border = "!" * (width + 2)
+    print(f"{YELLOW}{border}{RESET}")
+    for line in lines:
+        print(f"{YELLOW}! {line:<{width - 2}} !{RESET}")
+    print(f"{YELLOW}{border}{RESET}")