chore(release): prepare stable 0.1 (#17)

## Summary

Exit DomainKit's beta release channel and prepare the first stable
`0.1.0` release on npm's
`latest` tag. Add a complete stable changelog summary that explicitly
covers both Cloudflare and
Vercel.

## Release transition

| Before | After |
| --- | --- |
| `domainkit@0.1.0-beta.1` (`beta`) | `domainkit@0.1.0` (`latest`) |

## Validation

- `bun run release:check`
- Isolated `bun scripts/tegami.mts version` predicted `0.1.0-beta.1 →
0.1.0`
- Published beta consumer proof passed TypeScript, Node 24, Bun,
Promise, Effect, Cloudflare, and Vercel entry points
- Disposable Samva consumer proof passed API/storage typechecks and 10
focused integration tests