Guardrails for Candidate-History Frameworks: A Declaration Ledger for Representation, Records, Admissibility, and Probability

S0 v0.2a is a claim-control and declaration-ledger synthesis of four published guardrail papers in the Complete-History / Record-Capability sequence. Its purpose is not to propose a physical selector, probability law, Born-rule derivation, single-outcome actualization rule, measurement-problem solution, Bell/no-signaling result, or experimental prediction. Instead, S0 formulates a reusable ledger for separating representation, access/readout, record availability, admissibility, probability/weights, operational frequencies, Born/no-signaling gates, and actualization claims in candidate-history-type proposals. The synthesis organizes the public A-D1-B1-C0 sequence into four negative guardrails: reduced or coarse history structure is not a physical selector; recoverable-record diagnostics are protocol-relative; closure/admissibility is not a probability law; and decohered alternatives, accessible records, single-outcome actualization, and Born-compatible probability laws are distinct notions. The paper introduces a declaration profile, layer ledger, no-automatic-arrows rule, claim-license table, worked audit example, and claim-status classification for proposals that make stronger physical-selector, probability, Born-compatibility, record-actualization, or operational-testability claims. Passing the S0 ledger is not evidence that a proposal is true, empirically adequate, dynamically complete, or physically selected. It only means that the proposal has separated the relevant claim layers and made its additional assumptions or bridge principles explicit enough to be evaluated.This is Synthesis Paper S0 v0.2a in the Complete-History / Record-Capability working-paper sequence. It is a claim-control / declaration-ledger paper only. It introduces no physical selector, no probability law, no Born-rule derivation, no Bell/no-signaling result, no actualization rule, no quantum-mechanics replacement, and no experimental prediction. The uploaded source ZIP contains the LaTeX source. SHA256SUMS.txt provides file-integrity hashes for the uploaded PDF and source archive.