fix(ce-work-beta): use codex not codex exec for piped stdin delegation

`codex exec` does not accept `--approval-mode` flag. When piping a
prompt via stdin, use `codex --approval-mode full-auto --quiet`
directly (no `exec` subcommand).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: huntharo

plugins/compound-engineering/skills/ce-work-beta/SKILL.md

@@ -479,10 +479,11 @@ When external delegation is active, follow this workflow for each tagged task. D
    **Use `cat ... | codex`, not shell redirects.** Codex CLI rejects `< file` with "stdin is not a terminal". Always pipe:
 
    ```bash
-   cat /tmp/codex-task-XXXXX.txt | codex exec --approval-mode full-auto --quiet 2>&1
+   cat /tmp/codex-task-XXXXX.txt | codex --approval-mode full-auto --quiet 2>&1
    ```
 
-   Do not use: `codex exec ... < /tmp/codex-task-XXXXX.txt` (fails immediately).
+   Do not use `exec` subcommand with piped stdin — `codex exec` does not accept `--approval-mode`.
+   Do not use shell redirects (`< file`) — Codex rejects them with "stdin is not a terminal".
 
    Piping also avoids `ARG_MAX` limits that would occur if passing the prompt as a CLI argument.