Add Stage 8 holdout and emission ablation package

[Mmdabb]

Summary

• replace the QVDFE outlier screen with hard physical/range exclusions and a two-vote soft statistical screen
• add Stage 8 blocked-holdout calibration, structural validation, and B0-B3 emission-ablation code
• add the Stage 8b held-out emission supplement and generated tables
• add the standalone v12 empirical-section draft and its eight PDF figures
• add machine-readable Stage 8 results plus the handoff and numerical-progress records

The CBI Plus replacement files and tests/test_cbi_plus_fixes.py are intentionally excluded.

Why

The previous outlier screen excluded an episode when any single distributional flag fired, while NaN/inf and other out-of-range state values could pass ordinary comparisons. The new screen separates immediate physical/range failures from relational evidence that requires two agreeing soft flags. The additional experiment files provide a date-blocked 70/30 holdout and emission ablations over the frozen Stage 0-7 outputs.

Validation

• all five added/updated Python files parse successfully
• stage8_manifest.json parses successfully
• all 10 CSV artifacts load successfully
• all eight PDFs have valid PDF signatures
• every figure referenced by section_empirical_v12.tex is included
• all 32 committed Git blobs match the handoff files byte-for-byte

Review notes

• the v12 empirical section is added as a standalone draft and is not wired into main_v8.tex
• the supplied numerical artifacts come from the frozen prior pipeline outputs; a full Stage 2b-8 rerun remains a follow-up