👷 add npm + jsr publish workflows

[cowboyd]

Motivation

The repository was moved to thefrontside/freedom and needs CI/CD on par with thefrontside/clayterm: automatic verification on PRs (including dry runs of both publish pipelines) and tag-driven publishing of @frontside/freedom to npm and jsr.

Approach

Mirror clayterm's workflow set, adapted for a single-package, no-wasm repo:

• verify.yml — on push/PR to main. A test job runs deno fmt --check, deno lint, and deno task test. Dependent jsr and npm jobs then dry-run the publish pipeline against a synthetic 0.0.0-verify.0 version, so any packaging issue surfaces on the PR rather than at tag time.
• publish.yml — on v* tags. Dry-runs both registries, builds, then publishes to npm (via dnt) and jsr (after stamping the tag version into deno.json).
• preview.yml — per-PR previews via pkg-pr-new.

Two commits:

1. CI workflows + tasks/build-{npm,jsr}.ts + deno.json task wiring + .gitignore.
2. deno fmt reflow + an explicit Context<NodeImpl> annotation on NodeContext (required by jsr's no-slow-types lint), so verify is green on landing.

Possible Drawbacks or Risks

Publishing requires NPM_TOKEN and JSR_TOKEN repo secrets (or OIDC trust). Not yet configured.

TODOs and Open Questions

• set up npm provenance via OIDC.
• Add JSR_TOKEN repo secret