Make scene-spec the default Manim path for all clients

[jmjava]

Summary

• generate-all auto-runs scene-spec-generate when manim segments exist but animations/specs/*.scene.yaml is missing
• Retiming matches hyphenated / script labels to Whisper's single glued words (e.g. setup-agent-prompts.sh, version-controlled)
• CLI/README/AGENTS/dogfood hints document specs as the default; ASCII fix in _box docstring for manim_scene_lint

Test plan

• pytest tests/test_pipeline.py tests/test_scene_spec.py::test_sync_row_labels_hyphenated_label_matches_glued_whisper_word
• Fresh client with manim segments and no specs: docgen generate-all --skip-tts creates specs then compiles
• Existing specs: generate-all retimes without LLM unless --regen-scene-specs

Made with Cursor

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