Biological radical-pair systems operate at decoherence rates γeff = 3.25–4.55, far exceeding the entanglement-breaking threshold γc ≈ 0.3 (channel-model-dependent). Standard quantum error correction provably fails (Q1 = 0). We identify three escape routes: (i) motional narrowing from protein tumbling reduces γeff to 0.19–0.27 < γc; (ii) decoherence-free subspace encoding achieves F = 0.99 with 27 enzyme copies (assuming collective noise fraction fcoll ≥ 0.94); (iii) the Petz recovery map with a noisy nuclear-spin reference preserves concurrence C = 0.46 as an information-theoretic bound. Radical-pair quantum reservoir computing (QRC) performance degrades monotonically with noise and correlates with quantum resources (rQFI = −0.52); motional narrowing rescues QRC by 6×, though a classical echo-state network retains an advantage at current simulation scales. These results reframe the quantum brain hypothesis: not quantum computation, but quantum reservoir dynamics enhanced by biologically natural motional narrowing.