ci: automate npm publish on version tags via Trusted Publishing

[ScreamingHawk]

What

Adds automated deployment: pushing a v* tag now publishes @0xsequence/codegenie to npm.

• .github/workflows/release.yml — triggers on version tags; verifies the tag matches package.json, typechecks, builds, and runs npm publish via npm Trusted Publishing (OIDC). No NPM_TOKEN secret; provenance attestations are attached automatically.
• RELEASING.md — documents the one-time npm-side setup and the release procedure.

Blocked on npm-side setup

@pkieltyka — could you (or another package owner) add a Trusted Publisher on npmjs.com for @0xsequence/codegenie?

• Package → Settings → Trusted Publisher → GitHub Actions
• Organization: 0xPolygon, Repository: codegenie, Workflow: release.yml, Environment: (empty)

Until that's configured, the workflow will fail at the publish step (everything before it — version check, build — still runs, so a tag push can dry-run the rest).

Notes

• The full test suite isn't re-run at release time (it needs actionlint + Foundry); PR CI remains the test gate. The release workflow still typechecks and builds from scratch.
• Passes actionlint / pnpm run check:workflows locally.
• When the package moves out of the @0xsequence scope (per the README note), the trusted-publisher entry needs recreating on the new name.