feat: support calculated_measures and .all() in YAML config

[boringdata]

Summary

• Add calculated_measures section to YAML config for derived metrics that reference other measures by name (Support calculated measures (derived metrics) in YAML #202)
• Support .all() window aggregations in YAML calculated_measures for percent-of-total patterns (.all() for window aggregations not supported in YAML #115)

Example

measures:
  total_distance: _.distance.sum()
calculated_measures:
  avg_per_flight:
    expr: _.total_distance / _.flight_count
  pct_of_total:
    expr: _.total_distance / _.all(_.total_distance) * 100

Test plan

• test_yaml_calculated_measures — calc measures via YAML config
• test_yaml_calculated_measures_simple_format — simple string format
• test_yaml_all_window_aggregation — .all() percent-of-total in YAML

🤖 Generated with Claude Code

[boringdata]

Codex Review Summary

Codex (gpt-5.3-codex) reviewed this PR. The review findings were about proxy fallback code that is not part of this PR (the reviewer's checkout included files from PR #207).

This PR only modifies yaml.py (calculated_measures parsing, .all() support) and tests. No issues found with the actual changes. All 37 YAML tests passing.