main: keep only what reproduces the manuscript; everything else lives on dev

Removed from main (all preserved on the dev branch): the arXiv build and
its sources, design documents (blueprint, results summary, review responses,
essay drafts), tasks/ and CLAUDE.md, the cover letter and reference tooling,
two unused manuscript figures, and every experiment that feeds no figure or
number in the paper: the collapse null, the sexual-vs-asexual lineage, the
NK speciation variant, the 0.5B single-seed LLM prototypes, the compose and
society experiments with their calibration and pilot runs, and their
configs, runners, tests, figure scripts and PBS jobs. Their result bundles
are moved to results/_archive/ (ignored) so the parquets stay on disk.

Also: plot_llm_speciation reads the s{seed}/ layout; the mating-breadth
plot writes under its bundle name; Makefile targets reduced to the kept
experiments; REPRODUCING.md and README point to dev for the rest.

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

configs/llm/curriculum_v5_stop3.yaml

@@ -2,7 +2,7 @@
 # `society` arm except that recombination is switched off from generation 3 onward (`merge_until: 3`):
 # obligate merging at generations 0-2, none afterwards. This is the fixed "merge early, then stop"
 # schedule the veto arm must be compared against, because in the seed-1 veto run lineages declined
-# 1/3 of merges at generations 0-2 and 3/3 at 3-5. Pre-registered readout: tasks/prereg-llm-society-v4.md §8g.
+# 1/3 of merges at generations 0-2 and 3/3 at 3-5. Pre-registered readout: tasks/prereg-llm-society-v4.md on the dev branch §8g.
 experiment: llm_curriculum_v5_stop3
 kind: llm_curriculum
 base_model: Qwen/Qwen2.5-1.5B