The existential threat posed by large-scale quantum computers (LSQCs) necessitates the immediate and strategic replacement of classical public-key cryptography (PKC) across all critical security layers. Session security, which relies on the integrity and authenticity of state tokens in horizontally scalable architectures, presents a uniquely challenging migration vector. This paper delivers a comprehensive, sixty-page-equivalent technical analysis of the architectural integration of Post-Quantum Cryptography (PQC) into session token protocols. We conduct an in-depth evaluation of the NIST-standardized hash-based signature (HBS) schemes, focusing on the stateful LMS/XMSS and the stateless SPHINCS+. Our analysis includes formal security models, detailed performance profiling (including parameter-set specificity), and operational modeling of deployment architectures. We confirm that the stateless requirement renders LMS/XMSS nonviable for high-volume session signing. While SPHINCS+ solves the state dependency, its inherent large signature size (up to 41 KB) and signing latency preclude its direct use in standard HTTP session headers. We formally propose and validate a Dual-Layer Hybrid PQC Strategy that combines Kyber Key Encapsulation Mechanisms (KEMs) for transport security with high-entropy symmetric Message Authentication Codes (MACs) for token integrity, providing an immediate, performant, and quantumsafe solution, while reserving compact lattice-based signatures (Dilithium) for future direct token signing.