Add versioned ephemeral custody lifecycle

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a02669-87ee-7a31-b111-edc95a16e0fa

scripts/remote_exec.py

@@ -0,0 +1,43 @@
+#!/usr/bin/env python3
+"""Small, value-safe SSH argv transport shared by attended procedures."""
+
+from __future__ import annotations
+
+import shlex
+import subprocess
+from typing import Callable
+
+
+class RemoteExecutionError(RuntimeError):
+    pass
+
+
+def remote_command(argv: list[str]) -> str:
+    if not argv or any(not isinstance(part, str) or "\0" in part for part in argv):
+        raise RemoteExecutionError("remote argv must contain non-NUL strings")
+    return shlex.join(argv)
+
+
+def run_remote(
+    host: str,
+    argv: list[str],
+    *,
+    label: str,
+    input_text: str | None = None,
+    allow_missing: bool = False,
+    runner: Callable[..., subprocess.CompletedProcess[str]] = subprocess.run,
+) -> subprocess.CompletedProcess[str]:
+    if not host or any(character.isspace() for character in host):
+        raise RemoteExecutionError("remote host must be a single SSH destination")
+    completed = runner(
+        ["ssh", "-o", "BatchMode=yes", host, remote_command(argv)],
+        text=True,
+        capture_output=True,
+        input=input_text,
+        check=False,
+    )
+    if completed.returncode and not (allow_missing and completed.returncode == 1):
+        # Remote output may contain provider or application material. Keep the
+        # durable error value-safe and let an attended operator inspect locally.
+        raise RemoteExecutionError(f"{label} failed (exit {completed.returncode})")
+    return completed