Migrate Drying_Model state handling to StateLayout

[bernalde]

Parent: #118

Depends on the StateLayout infrastructure sub-issue and the focused drying initialization bug fix.

Scope

Migrate drying state initialization, model evaluation, and result retrieval to the shared state layout.

Acceptance criteria

• Replace memorized positional slices with layout-based access.
• Make every initialization branch use the same declared blocks.
• Add regression coverage for relevant drying modes.
• Demonstrate unchanged numerical results apart from separately tracked defects.