Gravity without Curvature and Scalar-Vector Unification

We introduce an inertial-oriented geometry (IO) unifying classical gravitation and internal electromagnetism without the need for a global metric. Built on three affine axioms (oriented structure, homogeneous Lagrangian, variational principle) and two laminarity conditions, IO features a privileged 1-form ω, its dual vector w, and a transverse hyperplane H = ker ω. Internal kinematics define an invariant ξ = |u|/c₀ and a general Lagrangian L(u) dependent on ξ. Directional organization involves a scalar operator and a unique potential Xµ = (Φ, A), universally coupled through µ_I = G/c₀². The dynamics for each species follow from two internal Poisson equations and a universal projective deviation law. A systematic five-step method covers weak-field, strong-field, post-Newtonian, wave, and cosmological regimes, reproducing without any free parameter the complete set of gravitational tests (1PN, gravitomagnetism, PPN, binary waveforms up to 3.5PN, Kerr dynamics, ΛCDM cosmology), and precisely reduces to the Maxwell–Lorentz equations when ∇Φ^(m) ≃ 0. IO makes explicit, falsifiable predictions testable by upcoming observations (LISA, Einstein Telescope, EHT+, Euclid/LSST), including a scalar gravitational wave mode with longitudinal memory, significant post-Newtonian dephasing, enhanced frame-dragging effects, and the strict equality µ_I c₀² = G. These observations will clarify whether IO is merely a mathematical redundancy or a genuine physical alternative to general relativity.