Generate assistant capability report from evidence

[tsotchke]

Summary

• add a deterministic capability/functionality report builder for assistant evidence
• regenerate the report from current raw, generalist, consistency, KDB, stress, and hardware-capture rehearsal evidence
• document the report refresh command and cover the builder in unit tests

Verification

• python3 scripts/build_assistant_capability_report.py --self-test
• python3 scripts/build_assistant_capability_report.py
• .venv-torch311/bin/python -m unittest discover tests
• python3 scripts/verify_assistant_packs.py
• .venv-torch311/bin/python scripts/build_preview_release.py --self-test
• .venv-torch311/bin/python scripts/verify_preview_artifacts.py
• LC_ALL=C LANG=C shasum -a 256 -c release sidecars