Existence of a classical (non-computer-assisted) proof of the Four Color Theorem

Construct a purely classical, human-checkable proof of the Four Color Theorem that does not rely on computer assistance.

Background

The Four Color Theorem inaugurated computer-assisted graph theory, with subsequent shorter and formally verified proofs. Nonetheless, the absence of a traditional, non-computational proof persists as a meta-level open challenge, underscoring foundational questions about proof verification and methodology.