Layer 1 core: Wright-Fisher knowledge-transmission model with E1-E2

Scaffold plus the Layer 1 analytical core and the first two experiments.

- knowledge/: truth, metrics, teachers (2.7.1 shared-switch construction),
  step, lineage, experiment, config, seeding (imported as `knowledge`).
- Validation spine green: neutral decay (Pred 1), fixation (Pred 2), exact
  mutation-drift equilibrium (Pred 3), union coverage (Pred 5). 68 tests pass.
- E1 reproduces tail-first collapse. E2 delivers the headline: a grounding
  phase boundary g* << 1, with stationary H tracking the exact H_eq closed
  form (g=0.005 -> 68% of truth diversity; g=0.05 -> 96%).
- Reproducibility: uv venv from a hash-pinned uv.lock is the source of truth;
  every run writes results.parquet + resolved_config.yaml + manifest.json
  (lib versions, git commit, sha256). Figures and manifests tracked; the
  large regenerable parquet is gitignored.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

configs/layer1/E1.yaml

@@ -0,0 +1,32 @@
+experiment: E1_reproduce_collapse
+seed: 20260704
+n_replicates: 100
+generations: 600
+
+# Null model (blueprint 2.5-E1): no grounding, single teacher, no selection.
+# Starting from the truth makes the collapse narrative clean -- the tail is lost first,
+# support shrinks to 1, forward-KL diverges, and H decays geometrically at rate 1/n.
+# (The decay law E[H_t]=H_0(1-1/n)^t holds from any start; see the validation suite.)
+truth:
+  K: 500
+  R: 1
+  tail: zipf
+  zipf_s: 1.1
+  tail_frac: 0.5
+  tail_threshold: 1.0e-3
+  init: truth
+
+dynamics:
+  n: 100                 # distillation sample size = drift strength
+  teachers: {K_T: 1, rho: 0.0, q: 1.0}
+  grounding: {m: 0, policy: proportional}
+  selection: {mode: none, novelty_alpha: 0.0}
+  remint: {enabled: false, period: null, H_gate: null}
+
+metrics:
+  kl_floor: 1.0e-9
+  support_eps: 1.0e-9
+
+# No sweep: a single condition.
+output:
+  dir: results/E1