docs: document the match predicate on generators and macros

[stijnvanhulle]

🎯 Changes

kubb-labs/kubb#3828 adds an optional match(node, ctx) predicate to Generator: a generator whose match returns false is skipped for that node entirely, instead of being called and bailing out itself. The same PR renames Macro's when gate to match for the same reason (when hadn't shipped in any release yet).

• reference/kit/generators.md: new "Scoping with match" section, with a short example
• guide/concepts/generators.md: a short conceptual pointer to it, next to the existing "What each method handles" section
• snippets/how-to/macros.md: when → match throughout (type definition, prose, and the enforce.ts example)

Depends on kubb-labs/kubb#3828 merging and releasing before match is real. No urgency to merge this ahead of that, but the content is accurate to the shipped API design either way.

✅ Checklist

• I have followed the steps in the Contributing guide.
• I am using USA English (serialize, color, center, canceled, analyze, license).
• I ran the humanizer check on any new documentation I wrote.

---

Generated by Claude Code

[changeset-bot]

⚠️ No Changeset found

Latest commit: 651a4cd

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.

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