fix(ce-work-beta): correct Codex delegation command and document pitfalls

Replace incorrect `codex --approval-mode` example with the tested
working invocation: `cat file | codex exec --skip-git-repo-check - `.

Add a pitfalls table documenting all five failure modes discovered
during testing: shell redirects, bare codex vs exec, wrong flags,
missing git repo check skip, and missing trailing dash for stdin.

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

Author: huntharo

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

@@ -472,16 +472,21 @@ When external delegation is active, follow this workflow for each tagged task. D
 
 3. **Write prompt to file** — Save the assembled prompt to a unique temporary file to avoid shell quoting issues and cross-task races. Use a unique filename per task.
 
-4. **Delegate** — Run the delegate CLI, piping the prompt file via stdin. Omit the model flag to use the delegate's default model, which stays current without manual updates.
-
-   **Use `cat ... | codex`, not shell redirects.** Codex CLI rejects `< file` with "stdin is not a terminal". Always pipe:
+4. **Delegate** — Run `codex exec` with the prompt piped via stdin. Use `exec` (not bare `codex`) for non-interactive delegation. Omit the model flag to use the delegate's default model, which stays current without manual updates.
 
    ```bash
-   cat /tmp/codex-task-XXXXX.txt | codex --approval-mode full-auto --quiet 2>&1
+   cat /tmp/codex-task-XXXXX.txt | codex exec --skip-git-repo-check - 2>&1
    ```
 
-   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".
+   **Codex exec pitfalls (all discovered during testing):**
+
+   | Pitfall | Error you get | Fix |
+   |---------|--------------|-----|
+   | Shell redirect `< file` instead of pipe | "stdin is not a terminal" | Use `cat file \| codex exec ...` |
+   | Bare `codex` instead of `codex exec` | Enters interactive mode, hangs | Use `codex exec` for non-interactive delegation |
+   | `--approval-mode` flag on `exec` | "unexpected argument" | `exec` has its own flags; `--approval-mode` is for bare `codex` only |
+   | Running outside a git repo | "Not inside a trusted directory" | Add `--skip-git-repo-check` flag |
+   | Forgetting `-` at end | Prompt not read from stdin | Trailing `-` tells `codex exec` to read the prompt from stdin |
 
    Piping also avoids `ARG_MAX` limits that would occur if passing the prompt as a CLI argument.