fix: qualify synonym tutorial and downloads for publication

[AlexMikhalev]

The synonym tutorial still described merged candidates, displayed a stale client version, and made a blanket local-data claim despite optional provider synthesis. This change distinguishes the original recording from released-binary evidence, fixes the privacy and version copy, and adds canonical/social metadata.

A downloadable reproduction kit contains the actual exported graph, plain/annotated brief, zero-match baseline, paired released outputs, captions and checksums. Original recording bytes and manifest are unchanged.

Validation: pinned Zola 0.22.1 build; all 16 Python tests; all 12 advertised stable download links; independent review and ZIP extraction using released grep 1.21.19 (0 baseline passages → 3 exact passages with the exported graph). Provider synthesis is retained from the separately verified release run, not rerun or relabelled here. Publication assertions now run on PRs as well as deployment.

[AlexMikhalev]

Independent Codex review of f03392d found no blocking issues. The reviewer independently ran pinned Zola 0.22.1 and all 16 tests, verified old demo bytes were unchanged, checked released evidence against saved outputs, and extracted the new ZIP to run released grep 1.21.19: zero baseline passages, then three exact passages with the exported graph. Existing synthesis citations match their source lines; provider synthesis was not rerun in this review.

Both GitHub CI jobs passed. This is an agent review, not a human approval. The repository requires one formal approving review, and the authenticated owner cannot approve their own PR. Under the owner's explicit instruction to fix and publish this rollout, the owner merge uses the repository's existing admin permission; branch protection is unchanged.