chore(ci): refresh models.dev snapshot in the release pipeline - #50011

Third piece after #50009 (refresh) and #50010 (cron). Makes publish.yml refresh the bundled models.dev snapshot before building, so every release ships the current catalog even if the last scheduled refresh was a while ago or a bot commit hasn't landed yet.

• The version job runs bun run update-models-snapshot once and uploads snapshot.txt as a models-dev-snapshot artifact.
• The three jobs that bundle @opencode/core — build-cli, build-node-app-archive, and publish (which builds the @opencode/core npm package) — download it before setup-bun/build, so all artifacts of one release carry an identical catalog.
• The refresh step is continue-on-error: true: a models.dev outage ships the committed snapshot rather than blocking the release (the step still shows as failed in the run).

The committed snapshot.txt is untouched by this workflow — nothing is written back to the repo — so from-source, embedded, and nix builds are unaffected; keeping the committed copy fresh is #50010's job.

This mirrors what dev had: the legacy CLI build fetched api.json at build time via packages/opencode/script/generate.ts and injected it as the OPENCODE_MODELS_DEV define. #41838 replaced that with the committed snapshot (so from-source and embedded hosts get a floor at all) but dropped the per-release fetch; this restores it on top.