Standardize summary output sections

[liuyewang]

Summary

• Standardize conversational reports around four sections: Today at a glance, What you did, App table, and Caveats.
• Preserve the same structure for unavailable ActivityWatch data and explicitly mark unavailable metrics.
• Allow reduced output only when the user explicitly requests a simpler or shorter response.

Validation

• python3 -m unittest discover -s tests -p 'test_*.py'
• git diff --check

Privacy impact

No collection or redaction behavior changed. The update only makes the default conversational presentation consistent and keeps the existing local-first privacy rules.