feat(publication): integrate Artifact DNA and AI candidates

[szmyty]

Closes #400

Summary

• let magazine artwork entries reference validated renderflow.artifact-dna/v1 sidecars
• add a typed, schema-bound renderflow.magazine-candidates/v1 envelope with deterministic asset-brief and metadata candidates
• preserve source/DNA digests, DNA extractor/policy/configuration evidence, compiler settings, validation, approval state, and explicit no-content-generation evidence
• add privacy, secret, protected-reference, direct-imitation/copyright, source-rights, and prompt/output hygiene gates
• register skill.magazine.candidates@1.0.0 and route optional enhancement only through the provider-neutral Add a model compatibility matrix and spec-driven AI skill runtime #396 runtime
• keep local/open models first-class, require explicit remote/privacy opt-ins, and keep missing AI capability non-fatal
• retain AI output as a separate review-required candidate instead of merging it into publication metadata
• add a redistribution-safe magazine DNA fixture plus local-only and optional-AI documentation

Focused validation

• changed Rust files formatted with rustfmt (no cargo fmt --all)
• cargo check --workspace --all-features --locked
• cargo test --package renderflow --lib publication::magazine --locked
• cargo test --package renderflow --lib ai::skill --locked
• cargo clippy --workspace --lib --bins --all-features --locked -- -D warnings -A clippy::too_many_arguments
• renderflow spec validate --config examples/magazine/renderflow.yaml
• renderflow ai skills validate
• deterministic magazine-candidate smoke test and byte-repeatability check
• optional-AI unavailable-path smoke test
• remote opt-in gate smoke test
• generated v2 schema synchronization and JSON/schema contract assertions

The full test suite and GitHub Actions were intentionally deferred for this infrastructure speed-run.

[devactivity-app]

Pull Request Summary by devActivity

Metrics

Achievements

• @szmyty
  Earned XP: 15⭐
  Check Your Progress