This synthesis document compresses the 35-paper Interior Observer (IO) corpus through Paper 35 v1.1 into a single overview written for working physicists arriving cold. The IO framework is built on two working premises: (1) the observable universe exists inside a Schwarzschild black hole, and (2) the physics inside the horizon is the same as the physics outside. From those premises, the framework derives a typed boundary-to-bulk projection architecture that yields cosmological observables across geometry, Big Bang Nucleosynthesis, recombination, the Hubble tension, and late-time evolution, with no fitted parameters. The overview leads with the cosmological lithium problem (Paper 24 v2.3): a branch-resolved A=7 mechanism gives D/H = -0.66σ, Y_p = +0.68σ, and Li-7/H = +0.46σ against current observations, all within 1σ at zero fitted parameters, with the nuclear isovector ratio c_n/c_p = 1+γ_BI² matching at 0.023%. Subsequent sections cover the framework's two premises and their corpus arc, claim-label discipline and methodology, the typed-compiler architecture, the major geometry and thermal results (T_obs = 2.7253 K at 0.3σ from FIRAS; n_s = 0.9639 at 0.24σ from Planck), the BBN scorecard, the six-method Hubble tension account (max residual 0.57σ across Planck, GW sirens, TRGB, TDCOSMO, SH0ES, and TRGB+SN), the late-time chain in which Λ drops out of the hidden-support acceleration equation, the reproducibility infrastructure (paper-versioned bundles with SHA256-pinned GitHub Releases), the open-problem frontier (with the baryogenesis source mechanism reduced to a spin^c residual class on the horizon U(1) bundle), and annotated reading paths into the corpus organized by research interest. This document introduces no new physics, theorems, derivations, or numerical claims. It organizes existing results from the IO corpus for first-encounter reading. Claim labels (DERIVED, DERIVED/SCOPED, DERIVED/CONDITIONAL, CONDITIONAL/CONSTRUCTED, RECONSTRUCTION) are preserved verbatim from the source papers and not flattened. All numerical values were verified against the current versions of Papers 1, 17, 21, 22, 23, 24, 25, 32, 34, and 35, and all reproducibility bundle SHA256 hashes were verified against live GitHub Releases. v1.1 — Synchronization sweep with current public state of the corpus. The Overview was originally produced when Paper 17 v1.4, Paper 22 v1.5, Paper 25 v1.2, Paper 32 v1.5, Paper 34 v1.1, and Paper 35 v1.1 were the active public bundles. Subsequent revisions — most importantly Paper 17 v1.5 introducing the FIRAS-Fixed Readout Normalization Theorem (Theorem 17.2) — required propagation. v1.1 brings the Overview current: the retired independent-CMB-temperature claim is replaced by the FIRAS-fixed observer-side optical readout family T_obs(R4) = T_IO × x^(R4 K_gauge) with R4_FIRAS = 1.0031 ± 0.0096 (Conditional_Verified on FIRAS via Premise 2; frozen, not retunable); cross-paper version references updated throughout to Paper 17 v1.5, Paper 22 v1.6, Paper 25 v1.3, Paper 32 v1.6, Paper 34 v1.2, and Paper 35 v1.2; reproducibility-bundle SHA256s and release tags updated; Paper 35 numerical values updated to inherit FIRAS-fixed R4 (η_late = 5.7475 × 10⁻¹⁰, ε₁ × κ_f = 5.904 × 10⁻⁸, with η_BBN = 6.151 × 10⁻¹⁰ invariant under consistent R4 repair). No new physics, no new theorem claims; this remains a synthesis document. See https://github.com/dfife/io-framework-public/tree/main for claim naming convention.