Phase 2: Add equation-level fidelity regression suite for optimizer and CMS updates

[georgepullen]

Purpose

Build an equation-fidelity regression suite so optimizer/CMS parity work does not drift.

Mandatory Reading (blocking)

First comment must summarize:

• reports/NL_IMPLEMENTATION_ORACLE.md sections 6.1.1-6.1.4 and 7
• tests/test_cms_delta_rule.py
• tests/test_selfmod_dgd_linear.py

Required Code Anchors

• tests/
• .github/workflows/ci.yml
• scripts/tests/ and/or scripts/checks/

Scope

• Add focused regression tests for:
  • delta_rule, dmgd_mlp, muon_ns
  • CMS projection mode
• Add test target (single command) for fidelity suite.

Deliverables

• New tests and CI/smoke command.
• Documentation for running fidelity suite locally.

Acceptance Criteria

• Tests fail when formula is intentionally perturbed.
• CI runs fidelity suite.
• First issue comment contains mandatory reading summary.