Add opt-in observed-run dossiers

[xtraid]

Summary

• add one opt-in atomic generator for self-contained run.json, fixed LaTeX, PDF, and hash-bound assets
• version one SAT and three distinct complete UNSAT cases and reuse the existing trace/static square/hex render chain
• add closed validators, Pages index, isolated pdfLaTeX smoke, and preserve the ordinary run path

Local gates

• make check: 151 Python tests and 17 C binaries
• renderer: 262 passed
• real pdfLaTeX smoke plus byte-identical repeat compilation
• strict GCC and Clang, ASan/UBSan/LSan, GCC analyzer, Memcheck, Cachegrind
• Pages, diff, secret scan, artifact cleanup

Evidence boundary

UNSAT traces are complete diagnostic executions, not mathematical proof certificates. Raw timings are environment-specific and excluded from deterministic snapshot identity.