upgrade: Button for Solid 2 (closes #655)

[devx]

Closes #655.

Summary

Upgrades `Button` for Solid 2.0 on top of @davedbase's #673 sweep. Suppresses STRICT_READ_UNTRACKED by extracting the ref callback with `untrack` to avoid reactive tracking of the ref prop.

Verification

• `pnpm -F @kobalte/core typecheck` — 0 errors (excluding pre-existing `minimal-dialog.test.tsx` hardcoded path)
• `vitest run src/button/button.test.tsx` — 15/15 passing

Changeset

`.changeset/upgrade-button-solid2.md` marks `@kobalte/core` as patch.

Notes

• Prior art: this pattern was validated in opencenter-cloud/kobalte@solid2-next (466/466 tests green).

[jer3m01]

Thanks for the PR!

In Solid 2 ref already handles the merging built in, mergeRefs will get removed once the port is over.
Not sure however of the exact syntax, I believe it's an array for ref (might need to test yourself or find it somewhere in the infinite discord discussion).