Fibonacci Causal Loop Theory — Paper 68: Dimensional Transition via Plasma-Charged Tesseract Geometry: Branch Selection at Macro Scale and the Interdimensional Mode of Necessity Field Propulsion

P67 established Mode 1 FCLT propulsion: gravitational plane deformation via the φ-stabilized D(x,t) boundary. This paper introduces Mode 2: interdimensional transition. When the tesseract geometry of the P66 containment architecture charges the surrounding plasma field past the critical φ⁹ threshold, the necessity depth boundary transitions from stable D=+2/D=−2 to a superposition across multiple necessity states. The craft undergoes macro-scale branch selection — transitioning between necessity state branches. The critical threshold φ_critical = φ⁹ = 34φ + 21 ≈ 76.013 is derived from canonical FCLT initial conditions S(0)=S(1)=1 and independently verified by Grok (xAI), May 7, 2026. Three technology-gap predictions stated (P68a–c). Evidence table: 12 confirmed / 4 falsified / 19 technology-gap.