TQNT-V5.21 — Selection rule Δc_min ≥ 22 derived from Bar-Natan Vassiliev invariants

TQNT-V5.21 derivation of the minimum crossing number Δc_min for spontaneous topological reconnection in dark matter pearls (Class A and E of V5.19). Four mechanisms evaluated: Q_phys conservation, Kanenobu-Murakami linking, Bar-Natan Vassiliev primitives, and SU(2)_135 modular fusion. Bar-Natan rule v_{c_i+c_j-2} = lowest non-zero primitive Vassiliev invariant: for paire amphichirale légère 6₃+6₃ (c=12), this gives Δc_min = 22. The four mechanisms are evaluated on the 21 amphichiral pairs (15 cross + 6 self). The minimum across all pairs is 22, saturated by (6₃+6₃ self), (4₁+8₃ self), (6₃+6₃ ∪ 4₁+8₃). Result: V5.21 redeems V5.20 against the Fermi-LAT EDGRB diffuse constraint (Δc ≥ 22 reduces cascade γ by 26 orders compared to Δc=10). Bar-Natan derivation is axiomatic, no new V5 parameter. Note: V5.21 is insufficient against Fermi-LAT line searches (require Δc ≥ 30); see V5p_erratum_F3 for the open F3 falsification. Commit 8743f4f. 20/20 pytest tests pass.