feat: warn on unread validation issues

[Rich-Harris]

Little quality of life improvement: if you neglect to handle validation issues, SvelteKit will warn at you in dev. If you have a form like this...

export const signup = form(
	v.object({
		user: v.object({
			name: v.literal('Dan', "If your name's not Dan, you're not coming in")
		}),
		password: v.pipe(v.string(), v.minLength(8, 'Password must have at least 8 characters'))
	}),
	(data) => {
		// ...
	}
);

...being used like this...

<form {...signup}>
	<input {...signup.fields.user.name.as('text')} />
	<input {...signup.fields.password.as('password')} />
	<button>sign up</button>
</form>

...then if you don't handle the issues you'll see this:

---

I didn't add a test because testing console logs is annoying and our test suite is already too slow and bloated — adding another one just for this felt like overkill.

---

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[changeset-bot]

🦋 Changeset detected

Latest commit: 46363d9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sveltejs/kit	Minor

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-15653-svelte.vercel.app/