Fix Svelte reactivity edge cases and panel state handling

[banjerluke]

I ran into a reactivity issue when using the Svelte integration in my project. I am a bit confused as to why this slipped through, since I tested things manually before submitting the first PR and I think I would've caught this bug... oh well, should be fixed now.

In fixing this (with Opus 4.6 and GPT 5.4) I also uncovered a couple minor issues that I also fixed in the Svelte integration.

Changes:

• return getter-backed DialKitValues from createDialKit so property reads stay reactive after $state reassignment (major issue)
• remove the old unused .current snapshot property from DialKitValues (dead code removal)
• restore base values when deleting the currently active preset so falling back to "Version 1" matches the actual panel state
• measure slider label/value widths reactively and adjust opacity accordingly
• normalize the remaining Svelte bind:this refs to $state<... | null>(null) so they match Svelte 5’s runtime shape and stop relying on non-reactive element locals
• Update: fixed some Svelte warnings that were harmless but annoying

[banjerluke]

I found another issue so I will fix it and then reopen this PR

[banjerluke]

False alarm. It wasn't working correctly in my project and it was driving me nuts, but eventually I figured out I was importing an older version. 🤦‍♂️

The latest changes (in this PR) are working just fine, and moreover I've confirmed that they are necessary to have DialKit work reliably in Svelte.

[joshpuckett]

@banjerluke I did a big refactor today and merged all other open PRs. Would you mind taking a look at the issues that were causing this (after updating to latest version), and then if still present, update this PR after rebasing? Thank you!

[banjerluke]

Sorry, took me a minute to get around to checking this and updating the branch, but I opened a new PR at #34 with the fixes (still necessary) and I did a quick test in my app with it too.