feat: add typed strategy metrics

[fallblu]

Summary

• add bounded typed numeric, string, and boolean strategy metrics with units, dimensions, and aggregation metadata
• publish scenario contract v16 and strategy protocol v14 while preserving legacy metric encoding for older contracts
• extend conformance fixtures, documentation, deterministic journals, and compatibility tests

Test plan

• make check
• make coverage
• .venv-schema/bin/python test/validate_contract_conformance.py
• explicit v16 scenario/journal and strategy v14 schema validation

Relates to #39.