Cosmological Constant from S³ Geometry: A Parameter-Free Prediction

We show that the present-day vacuum-energy density follows from a single geometric postulate Ti² + Ci² = 1 on S³, with equipartition coupling α = √3/2. The bare prediction matches Planck 2018 to +9.4% with zero free parameters. Two structural corrections reduce the residual to +0.69% (0.64σ). The 10¹²⁰ cosmological constant problem is recast as a geometric projection problem. Full framework: https://doi.org/10.5281/zenodo.19503166OSF: https://osf.io/m6nd9/