Rename neural experiments to descriptive paths (drop N* codes)

configs/neural/{N0,N1,N2,N5}.yaml -> {bridge,collapse,grounding,architectures}.yaml,
results dirs likewise. Updated experiment/output.dir fields, comments/docstrings, and
docs; regenerated the four result manifests (now carrying the real git commit). No
functional path resolution referenced the codes (the Makefile globs configs/neural/*.yaml
and tests use inline configs), so nothing breaks. 92 tests green.

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

configs/neural/N2.yaml

@@ -1,50 +0,0 @@
-experiment: N2_grounding_phase_boundary_neural
-kind: gen_lineage
-seed: 20260704
-n_replicates: 5
-
-# N2 (Layer 1.5 headline, maps to Layer-1 E2): the grounding phase boundary in REAL weights.
-# Sweep the grounding fraction g = m/(n+m) and locate the neural critical g* at which
-# stationary diversity is restored. Layer 1 found g* = 0.048 << 1. The neural regime (finite
-# model capacity, a smaller K so gen-0 fidelity holds) will not reproduce that value exactly
-# -- the claim is directional (blueprint 3.5): a critical g* << 1 exists in trained weights,
-# i.e. a little grounding protects most of the diversity. Falsifier: stationary H flat in g,
-# or only restored as g -> 1.
-generations: 30
-
-synthetic:
-  K: 256
-  R: 1
-  tail: zipf
-  zipf_s: 1.3
-  tail_frac: 0.5
-  tail_threshold: 1.0e-3
-  init: truth
-  style_len: 3
-  style_vocab: 5
-  id_base: 2
-
-model:
-  kind: rnn
-  hidden: 128
-  embed: 24
-  epochs: 25
-  lr: 2.0e-3
-  batch_size: 256
-  n_eval: 12000
-
-dynamics:
-  n: 200
-  grounding: {m: 0, policy: proportional}   # m overwritten per g by the sweep
-  remint: {enabled: false, period: null, H_gate: null}
-
-metrics:
-  kl_floor: 1.0e-9
-  support_eps: 1.0e-9
-
-sweep:
-  - param: g
-    values: [0.0, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2]
-
-output:
-  dir: results/N2