[refactor] simplify cut-criteria scripts (drop base64, single Python)

[trilamsr]

PR #374 uses base64-encoded TSV rows in cut-criteria-status.sh to survive embedded newlines. Bash macOS-3.2 compat tax.

Asks:

• Replace 3 bash scripts (status.sh + render.sh + status_test.sh) with a single Python module scripts/cut_criteria.py exposing status() + render().
• Drop base64; multi-line shell snippets get passed as native Python strings.
• Add YAML schema validation step.
• Drift gate: git status -s docs/v1-rc1-cut-criteria.md post-render (simpler than tmp-diff).

Estimated: ~200 LOC delete + clarity win.

Tracked from: PR #374 reviewer + user feedback ("over-engineered?").