feat(migrate): prepare-ai-migration for sk3

[manuel3108]

This is something that was discussed weeks ago in discord. The idea is to provide the ai with hints what still needs to be migrated, because it was not statically analyzable or not enough users will be encountering this.

If we decide to move forward with this, we should follow this list: #1124 (comment)

The question is - do we want to move forward with this? I like the idea, but im not too sure the acceptance will be there and its worth the effort. It will still require us to go through the relevant breaking changes and curate them manually. The two migration tasks for testing were generated by ai, but both had fatal flaws that i needed to correct to be correct and clear checks.

Also i hate the current wording, prepare-ai-migration is the best i came up, but i still hate it. Also the "migration tasks" feel weired, since this is already a task so we would technically have subtasks, which are probably going to cause even more confusion.

What do you think?
If someone wants to pick it up from here - feel free.

Description

Checklist

• Update snapshots (if applicable)
• Add a changeset (if applicable)
• Allow maintainers to edit this PR
• I care about what I'm doing, no matter the tool I use (Notepad, Sublime, VSCode, AI...)

[pkg-svelte-dev]

Install the latest version of sv from 3720bdf:

pnpm add https://pkg.svelte.dev/sv/c/3720bdf5c1c88ee54f04ab118687dac3c822cb86

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/cli/pr/1239

[changeset-bot]

⚠️ No Changeset found

Latest commit: 3720bdf

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-cli-1239-svelte.vercel.app/

[dummdidumm]

I think this is a great idea. That way you could run a migration from this prompt: "Use npx sv migrate sveltekit-3 to migrate. This will automatically update code for some breaking changes and give you instructions for the rest. Follow these instructions to complete the migration.".

I would call this "collect-migration-instructions".