fix: require monthly shadow build and deterministic tiebreak

[Pigbibi]

Summary

• run the monthly shadow build wrapper in the publish workflow so official_baseline and challenger outputs are generated every cycle
• add a deterministic ranking tie-break based on confidence, liquidity stability, volume, then symbol
• record the tie-break rule in docs and cover it with tests

Verification

• uv run --with pandas==2.3.3 --with numpy==2.0.2 python -m unittest tests/test_ranking.py tests/test_monthly_publish_workflow_config.py tests/test_monthly_build_telegram.py tests/test_monthly_review_briefing.py tests/test_shadow_release_history.py tests/test_monthly_report_bundle.py tests/test_post_monthly_ai_review_comment.py
• uvx ruff check src tests scripts
• ruby -e 'require "yaml"; YAML.load_file(".github/workflows/monthly_publish.yml"); YAML.load_file(".github/workflows/ai_review.yml"); puts "yaml ok"'