fix(sveltekit): use afterNavigate for SvelteKit 2 and 3

[CNSeniorious000]

Problem

SvelteKit 3 removed the $app/stores module. injectAnalytics imported page from it and called page.subscribe(), which throws at runtime:

Uncaught (in promise) Error: https://svelte.dev/e/kit/app_stores_removed
    at injectAnalytics (index.mjs)

This crashes hydration for any SvelteKit 3 app using injectAnalytics.

Fix

• Use afterNavigate from $app/navigation to observe completed navigations without patching the global History API
• Keep the existing /sveltekit entry and update peerDependencies to ^2.12 || ^3
• Register injectAnalytics from a component initialization, as required by SvelteKit's afterNavigate lifecycle API
• Update the SvelteKit demo and README to use src/routes/+layout.svelte

afterNavigate is available in SvelteKit 2.12 and 3. Its callback receives the completed destination, so page views use the final { route, path } values.

Notes

• $app/environment is still used for browser; it is deprecated in SvelteKit 3 but not removed until SvelteKit 4
• Consumers should call injectAnalytics during component initialization, for example from +layout.svelte

[vercel]

@CNSeniorious000 is attempting to deploy a commit to the Analytics Test Projects Team on Vercel.

A member of the Team first needs to authorize it.