feat(node): add Bun support in runtime, CI, and docs

[RtlZeroMemory]

Summary

• add first-class Bun support coverage to @rezi-ui/node (runtime, CI, and docs)
• fix Bun worker backend shutdown behavior so stop()/exit completes reliably
• extend CI and docs to cover Bun usage alongside Node
• document install/quickstart/package guidance for Bun
• enable Material icon shortcode rendering in docs (pymdownx.emoji) so GitHub Pages cards render correctly

Runtime Change

• packages/node/src/worker/engineWorker.ts
• On Bun runtime, force worker process exit after shutdownComplete + parentPort.close() to avoid hanging worker teardown.

Validation

• bun run lint
• bun run typecheck
• bun run build
• bun run test
• bun run test:e2e:reduced
• Bun worker-mode smoke (with native shim): start/getCaps/stop completes