feature/jax: drop finished-investigation config graveyards (~12k yaml lines)

_b256_run/_b256_probe/_chunkwise/_xl_production/_bench6/_bench12/_gpt2xl_ab/
_resumption_validation — full dumped ExperimentConfigs of completed sweeps,
several for the carved-out subsystems; referenced nowhere. SPEC §9 gets a
note that n-pool ground-truth pointers refer to the other lineage.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: ocg-goodfire

nano_param_decomp_jax/jax_single_pool/SPEC.md

@@ -284,6 +284,9 @@ is global-batch math. This section is the whole answer to "now shard it":
 
 ## 9. Non-normative: torch ground-truth pointers & rationale
 
+Pointers into the n-pool subsystems (`three_pool/`, `param_decomp_lab/metrics/`)
+refer to the `feature/fsdp-lm-trainer` lineage — those trees are not on this branch.
+
 | spec | torch source |
 |---|---|
 | §4.1 site/forward, routing | `param_decomp/components.py` (`LinearComponents.forward`), `param_decomp/masks.py` |