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>

.gitignore

@@ -0,0 +1,13 @@
+# Environments
+.venv/
+__pycache__/
+*.pyc
+.pytest_cache/
+
+# Results: the large data artifact (results.parquet) is regenerable and gitignored;
+# the reproducibility metadata (manifest.json with content hashes, resolved_config.yaml)
+# and the figures (PNG/PDF) are tracked so the paper's figures live in the repo.
+results/**/*.parquet
+
+# OS / editor
+.DS_Store