The Informational Dark Sector: A Damkohler-Regulated Scalar Field That Recovers LCDM and Reproduces the Cosmological Constant

We present GUBIM (Grand Unified Brane-Informational Model), an effective kinetic framework in which dark matter and dark energy emerge as two regimes of a single informational scalar field Phi, differentiated by the cosmological Damkohler number Re -- the ratio of the informational reaction rate to the Hubble expansion rate. The dark-sector coupling is obtained from the Boltzmann collision integral with a Breit-Wigner cross-section, yielding Q = 3H rho_tot epsilon_m epsilon_DE / (1 + Re^2). This bimolecular interaction exhibits Le Chatelier saturation: at high Re (early universe), Q -> 0 and the background equation of state approaches w -> -1, recovering LCDM automatically. The dark-matter-like phenomenology at galactic scales arises from the perturbative clustering of Phi, not from the background w(z). LCDM was not assumed; it emerges as the Re -> infinity limit. Validation against 1094 data points (cosmic chronometers, Pantheon+ SNIa, DESI BAO, CMB distance priors) yields a statistical tie with LCDM (Delta chi^2 = -2.63, Delta AIC = -0.63). Full CAMB integration produces CMB power spectrum deviations below 1.63% at all multipoles. The background growth suppression gives sigma_8(GUBIM)/sigma_8(LCDM) = 0.989 (1.1% suppression), placing GUBIM in the direction favored by weak-lensing surveys. Gravitational waves propagate at c_T = c exactly. The framework offers candidate explanations for features that LCDM treats as free inputs: (1) rho_Lambda predicted to 0.23% via Landauer erasure at the Hubble horizon; (2) w ~ -1 from near-complete informational equilibration; (3) a common origin for dark matter and dark energy (one field, different Re regimes); (4) Milgrom's a_0 derived to 0.22% as a_0 = c H_0 sqrt(4/3) / (2 pi); (5) the coupling constant alpha_0 = 7.71 derived from Verlinde-Zurek modular fluctuations to 0.81%; (6) a geometric slow-roll bound that DESI DR1 violates and LCDM satisfies only trivially. Testable prediction: w_0 = -0.941 +/- 0.03 for Euclid/DESI DR3. This version supersedes v5 ("Dark Matter as a Dissipative Informational Condensate"). Major additions: Boltzmann-derived Q interaction, Gamma_0 = 1/H resolution, multi-catalog SNIa analysis (Pantheon+/DES/Union3/JLA), CAMB sigma_8 benchmark, holographic Q derivation, MOND derivation (companion paper), Verlinde-Zurek alpha_0 derivation (companion paper), theory status table.