fix(cron): skip NUL-bearing remote fallback content in lifecycle guard

[33hodl]

Summary

Harden the reusable gateway-lifecycle guard against NUL-bearing remote fallback content:

• Skip the remote-read fallback for referenced script paths containing an embedded NUL byte (machine code tokenized into a bogus path by the recursion).
• Treat NUL-bearing text returned by a remote fallback reader as binary — "nothing to scan" — mirroring the local binary skip, instead of tokenizing machine code and risking false blocks or ValueError crashes.
• Real remotely-read shell scripts containing lifecycle commands remain blocked.

Why

Upstream #77703 fixed the terminal_tool path (its _read_script_in_env pre-filters binary output); this diff sits on top of that work. However, the reusable contains_gateway_lifecycle_command_or_referenced_script API accepts an arbitrary read_remote_script callback and can be called directly. Raw NUL-bearing fallback bytes were still treated as shell text, so a binary containing lifecycle-looking strings could false-block a benign command. This makes the guard itself robust regardless of caller pre-filtering.

Validation

• pytest tests/hermes_cli/test_gateway_restart_loop.py -q -o 'addopts=' — 86 passed, including two new regressions:
  • raw binary fallback reference is skipped (no false block);
  • a real remote shell script containing a lifecycle command is still blocked.
• Full-repo Python compile + import smoke checks.
• Desktop TypeScript typecheck and Electron platform suite.
• Web check (tests/typecheck/lint) and production build.
• git diff --check clean.
• Deployed and verified on the production backend: serve healthy, gateway running, Telegram connected, auth boundary intact.

[kshitijk4poor]

Closing as superseded by #80258, which fixes this whole bug class architecturally rather than per-callsite: path candidates are sanitized once at the ingestion boundary (NUL/empty/unexpandable tokens rejected before any OS call), text from any read_remote_script callback is sanitized at the recursion boundary (NUL = binary = nothing to scan; >1 MiB = fail closed), the remote fallback read is bounded at the source (head -c, so oversized binaries never cross the wire), and the public guard is total by construction — an unexpected walk failure logs and falls back to the direct-scan verdict instead of breaking every terminal command.

Your report and fix targeted a real member of this class — thank you. The per-callsite patches kept leaving sibling frames exposed (#76762 → #77703 → #77780 → #78256 each crashed one frame away from the previous fix), which is why we went with the boundary fix instead of merging the fragments individually. #80258 carries regression tests for the NUL-path, binary-callback, oversized-read, unset-HOME, and walk-crash cases plus an adversarial never-raises sweep.