The gateway terminal guard crashed with 'ValueError: embedded null byte'
(command never ran, exit_code -1) when a command invoked an ELF binary by
full path. _read_referenced_script correctly rejects the binary locally
(NUL in first chunk), but the read_remote_script fallback
(_read_script_in_env) then re-read the SAME file's bytes without a NUL
guard, decoded them, and fed machine code back into the scanner, which
re-tokenized it into a bogus NUL-bearing path and crashed at os.open.
- _read_script_in_env: skip content containing a NUL byte on both the
local-read and remote-cat branches (mirrors _read_referenced_script:
a binary is nothing to scan), so binary never re-enters the guard.
- _read_referenced_script: tolerate ValueError from os.open on a
NUL-in-path, alongside the existing OSError guard, so the guard can
never crash the terminal tool regardless of input.
Extends the #76762 NUL-safety fix (local path only) to the gateway's
remote-read fallback path.