Create models/ subpackage with backward-compatible imports

[Hugo-W]

Create models/ subpackage with backward-compatible imports

Description

pyeeg/models.py is large (1102 lines) and contains multiple model families. Need to split it while maintaining backward compatibility.

Tasks

• Create pyeeg/models/ subpackage directory
• Create pyeeg/models/init.py
• Split pyeeg/models.py into:
  • pyeeg/models/trf.py (TRF-specific logic including TRFEstimator)
  • pyeeg/models/var.py (VAR model fitting logic)
  • Other modules as needed for clean separation
• In pyeeg/models/init.py, re-export all classes and functions to maintain pyeeg.models.TRFEstimator and similar import paths
• Update pyeeg/init.py imports if needed

Acceptance Criteria

• pyeeg.models.TRFEstimator still works (backward compatible)
• All existing import paths preserved
• models.py either becomes a compatibility shim or is removed
• Code is better organized with clear responsibilities

Priority

Medium

Dependencies

• Issue De cheveigne cca forms #3 (Stabilize public API) should be completed first
• Issue Audit docs/source/ for naming consistency #5 (solver consolidation) should be completed first

Epic

Modularization

Source

NEXT_STEPS.md Step 4, TODO.md Section 2