fix(solid-email): support workerd-safe root exports

[Akin01]

Summary

• Make @akin01/solid-email root exports resolve to the SSR/email build for server, Workerd, worker, and edge-like conditions while browser conditions resolve to the DOM preview build.
• Align Tailwind and render CJS/ESM paths on Solid's server runtime and CSS Tree's Workerd-safe dist ESM entry.
• Add Cloudflare TanStack Start e2e coverage plus docs, skill updates, bundle-size refresh, and changelog related commits.

Closes #12.

Verification

• pnpm test
• pnpm test:e2e
• pnpm typecheck
• pnpm build
• pnpm lint

Checklist

• Tests or examples cover the changed behavior.
• Types were checked without suppressions.
• Public API changes are reflected in docs or examples.