feat: show legacy slices in slice list and type view

[angeloashmore]

Related: DT-3535

Description

Before this PR, the CLI ignored legacy slices, the slices that the Legacy Builder defines inside a type. For example, slice list did not show them, and slice view hero on a legacy slice failed as a CLI bug.

After this PR, slice list and type view mark legacy slices, and slice list --legacy lists only them. Commands that edit a slice say when it is a legacy slice.

NAME      ID        DEFINED IN
Hero *    hero      blog_post
Quote *   quote     blog_post

* Legacy slice. The CLI cannot edit legacy slices.

Upgrading legacy slices is in #388, which builds on this PR.

Checklist

• If my changes require tests, I added them.
• If my changes affect backward compatibility, it has been discussed.
• If my changes require an update to the CONTRIBUTING.md guide, I updated it.

Preview

How to QA ¹

In a project with legacy slices, run npx prismic slice list, npx prismic slice list --legacy --json, and npx prismic type view <type>.

🤖 Generated with Claude Code

https://claude.ai/code/session_01H4jg7fmGVLhLJjo27eC7Mj

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Note

Low Risk
Read-only listing and clearer errors for slice lookup; no changes to model sync, auth, or write paths beyond messaging.

Overview
Legacy Builder slices embedded in custom types are no longer invisible in the CLI. getLegacySlices scans slice zones for non-SharedSlice choices and powers the new behavior.

prismic slice list merges shared slices with legacy ones in a table (NAME, ID, DEFINED IN), marks legacy rows with *, and adds --legacy (including JSON with definedIn / sliceZone). prismic type view lists each slice zone’s choices and asterisks legacy entries, with a short footnote when the type contains any.

Adapter.getSlice now detects a legacy ID and fails with a CommandError explaining that the CLI cannot edit legacy slices (e.g. slice view hero), instead of a generic not-found error.

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