Implement-review changed-file lint recipe is not portable to zsh

Observed from the generated implement-review guidance during #2658 (TF-036).

## Reproduction

Under zsh with multiple changed Python files:

```zsh
CHANGED_SRC=$(git diff --name-only ...HEAD -- "*.py")
uv run ruff check $CHANGED_SRC
```

Ruff receives one newline-containing filename and reports E902 because zsh scalar expansion does not perform Bash-style word splitting. An array or `xargs` invocation passes.

## Expected

Generated shell recipes should either declare the required shell or use a portable array/null-delimited form that works under supported operator shells.

Start with the generator for the implement-review guidance described in the issue, then reproduce the recipe under zsh using multiple changed Python files. Check how CHANGED_SRC is expanded before Ruff runs; done means the generated recipe works under supported shells without E902, or explicitly declares its required shell.

Written by the indexing model from the issue text.