chore: add project readiness checks

[No1Hoo]

Summary

• Add CI covering Python install/tests/ruff and frontend lint/build.
• Keep VoicePanel state aligned with derived script lines after clearing the editor.
• Document run modes, verification commands, audit policy, and manual UI regression checks.
• Preserve generation progress after a partial failure so users can see how far generation got.

Test Plan

• python3 -m venv .venv && .venv/bin/python -m pip install -e '.[dev]'
• .venv/bin/python -m pytest -q
• .venv/bin/python -m ruff check .
• cd frontend && npm ci
• cd frontend && npm run lint
• cd frontend && npm run build
• Browser automation: load demo script, clear editor, verify footer counts reset and VoicePanel returns to empty state

Notes

• npm audit still reports the known Next.js/postcss moderate advisory; this PR documents why not to use npm audit fix --force.