[tugrapaydiner]

Consolidated integration into main

This PR is the single integration point for the completed exact-query line and supersedes stacked drafts #60, #61, #62 and #63.

It includes:

• exact mixed SAT/UNSAT queries with complete witnesses or portable contradiction proofs;
• prepared and automatically selected native execution modes;
• independent native and standard-library replay/verification;
• a versioned installed spectra.exact API and CLI support;
• proof-carrying exam-repair application support;
• strict ITC-2007 parsing and hard-constraint validation;
• prospective set9/set10/set12 transfer evidence across Linux x86, native ARM64 and supported Python versions;
• Windows build and functional coverage plus sanitizer coverage;
• preserved negative results, failed attempts and claim boundaries.

Current head: 13d1d4192e97a4e372ac4aac7743a88b55e814bc.

The head is a descendant of current main and is 90 commits ahead with no missing main commits. Current head workflows completed successfully:

• exact-public-api
• public-package
• Query runtime checks

The merge preserves the work as opt-in, verified functionality. It does not claim universal speed superiority, operator adoption, outside replication, or a solution to unrestricted timetabling. After this integration, the stacked drafts will be closed as superseded and obsolete research PRs will be archived rather than left open indefinitely.