Layer 1 complete: E3-E6 + E2 analysis add-ons

Finishes the Layer 1 analytical core. All six experiments run with honest,
publication-quality figures; 71 tests green.

- E3 region-matched grounding: `grounding.exercised` knob + per-region tail
  survival. Matched holds the exercised region's tail (0.49) where uniform
  spreads thin and lets it collapse (0.07).
- E4 multi-teacher recombination: `run_coverage` runner. Union coverage matches
  U(K_T,rho,q) exactly. Finding: mean-mixture distillation shows NO surviving
  benefit (a conservation law — 1/K_T dilution cancels the union gain); a
  union-preserving max-merge (M2N2-style) does. E4 reports both operators.
- E5 QD vs greedy: greedy drives fixation (H~0.01); QD holds H at 0.48-0.88,
  rising with the novelty exponent.
- E6 re-mint gate: `arm` multi-override sweep. Re-minting a collapsed lineage
  locks in divergence of KL-to-original; gating on diversity prevents it.
- E2 analysis add-ons (from the companion work order, numbers verified): new
  analysis.py (reduce_to_stationary, critical_grounding with bootstrap CI ->
  g*=0.048, 95% CI [0.047,0.050]); tail_band_metrics + per-band logging; the
  E2 figure rebuilt as a 2x2 (defined g*+CI, g=0 flagged as a finite-time
  artifact, tail item-vs-mass, per-rarity-band panel). Uses truth-mass-weighted
  tail coverage rather than the raw (martingale) tail_mass.

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

results/E1/resolved_config.yaml

@@ -1,37 +1,6 @@
 experiment: E1_reproduce_collapse
 seed: 20260704
 n_replicates: 100
-grid:
-- label: {}
-  lineage_cfg:
-    truth:
-      K: 500
-      R: 1
-      tail: zipf
-      zipf_s: 1.1
-      tail_frac: 0.5
-      tail_threshold: 0.001
-      init: truth
-    dynamics:
-      n: 100
-      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
-    generations: 600
-    metrics:
-      kl_floor: 1.0e-09
-      support_eps: 1.0e-09
 source_config:
   experiment: E1_reproduce_collapse
   seed: 20260704
@@ -66,3 +35,34 @@ source_config:
     support_eps: 1.0e-09
   output:
     dir: results/E1
+grid:
+- label: {}
+  lineage_cfg:
+    truth:
+      K: 500
+      R: 1
+      tail: zipf
+      zipf_s: 1.1
+      tail_frac: 0.5
+      tail_threshold: 0.001
+      init: truth
+    dynamics:
+      n: 100
+      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
+    generations: 600
+    metrics:
+      kl_floor: 1.0e-09
+      support_eps: 1.0e-09