Manuscript revision and pending experiment work, snapshot before restructuring

Clarity pass over the main text (36-item audit), Discussion rewrite and cut,
acknowledgements, Souly et al. as ref 62, lettered SI panels, model section
moved under Results; plus the untracked curriculum/society/compose/smol
configs, runners, figures, stats and tests that the SI already cites.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y64o8FKP7rCuXzC48pxpMm

figures/plot_E2.py

@@ -17,7 +17,7 @@ import matplotlib.pyplot as plt
 import numpy as np
 
 sys.path.insert(0, str(Path(__file__).parent))
-from _figlib import load_bundle, mean_ci, savefig  # noqa: E402
+from _figlib import load_bundle, mean_ci, savefig, letter_axes  # noqa: E402
 
 sys.path.insert(0, str(Path(__file__).parents[1] / "src"))
 from knowledge.analysis import critical_grounding, reduce_to_stationary  # noqa: E402
@@ -88,7 +88,7 @@ def main(results_dir: str = "results/E2") -> None:
     ax.errorbar(mg, Mm, yerr=Mci, fmt="o-", color="#9467bd", capsize=3,
                 label="tail truth-mass alive")
     ax.set(xlabel="grounding fraction $g$", ylabel="fraction of tail retained",
-           title="Tail stays largely unrescued at feasible g\n(rises with g; motivates E4/E6)")
+           title="Tail stays largely unrescued at feasible $g$\n(rises only slowly with $g$)")
     ax.legend(frameon=False, fontsize=9)
 
     # Panel D: per-rarity-band survival across g (band 0 = rarest)
@@ -106,9 +106,8 @@ def main(results_dir: str = "results/E2") -> None:
            title=r"Per-rarity band: the $m\,p^*_i\gtrsim1$ threshold (deep lags)")
     ax.legend(frameon=False, fontsize=8)
 
-    fig.suptitle("E2 — a critical grounding ratio $g^\\star \\ll 1$ rescues diversity; "
-                 "the deep tail needs recombination", y=1.0, fontsize=13)
     fig.tight_layout()
+    letter_axes(fig)
     savefig(fig, results_dir, "E2")