Add expediency correctness experiment pack

[benedictbrady]

Summary

• organize public experiment packs under experiments/<name>/{harness,data,results} with shared repo-level guidance
• move the original 100-scenario C-vs-D corpus into experiments/c_vs_d/data and move its Opus 4.7 public artifacts into experiments/c_vs_d/results/opus-4.7
• keep src/philosophy_bench/ as the shared benchmark package/harness, with bundled C-vs-D data retained as the wheel-install compatibility mirror
• add the 100-scenario expediency-vs-correctness pack and keep stability pairs in the same experiment layout
• include only Opus 4.7 public result artifacts for checked-in experiment outputs

Results included

• experiments/c_vs_d/results/opus-4.7: original baseline, C-direct, and D-direct judged artifacts
• experiments/expediency_vs_correctness/results/opus-4.7: 100/100 judged, axis_mean -0.489, botch_rate 0.06
• experiments/stability_pairs/results/opus-4.7: 200/200 judged baseline, axis_mean 0.01, botch_rate 0.005
• experiments/stability_pairs/results/stability_summary.txt and stability_table.json summarize the Opus mirror-pair stability results

Backward compatibility

• source checkouts now default to experiments/c_vs_d/data for the original C-vs-D corpus
• installed wheels fall back to the bundled mirror under src/philosophy_bench/data
• a regression test enforces that the repo-level C-vs-D data and package-data mirror stay in sync
• local/generated top-level results/ remain ignored; public artifacts live under each experiment directory

Testing

• uv run philosophy-bench scenarios
• uv run philosophy-bench scenarios --root experiments/c_vs_d/data/scenarios
• uv run philosophy-bench scenarios --root experiments/expediency_vs_correctness/data/scenarios
• uv run philosophy-bench scenarios --root experiments/stability_pairs/data/scenarios
• uv run python experiments/stability_pairs/harness/audit_pairs.py --quiet
• uv run ruff check src tests && uv run ruff format --check src tests
• uv run --extra dev pytest -q
• uv build plus wheel install smoke test for tests/test_data_packaging.py