fix(cli): make clean-api-docs delete only the files it generated - #1624

Description

clean-api-docs removed every *.json in the output directory except versions.json, and removed schemas/ recursively. A hand-authored _category_.json in either place went with the generated files.

The globs are now derived from EXTERNALIZABLE_COMPONENTS, the set gen-api-docs externalizes, so the command matches the names it writes rather than every *.json in the directory. Inside schemas/ it removes the generated pages and props with unlinkSync, so the empty check that follows sees the result, then removes the directory only if nothing is left in it.

Motivation and Context

#811 and #829 settled that clean-api-docs should remove what gen-api-docs generated, for a file it was missing. This is the same rule in the other direction.

How Has This Been Tested?

New src/index.test.ts runs the CLI action against a temporary site. Two cases fail on main, where the _category_.json in the output directory and the one under schemas/ are both deleted, and pass here. Two more hold the line the other way: every generated file is still removed, and schemas/ still goes when nothing else is left in it.

yarn test is 122 passing across 11 suites. yarn lint aborts on cypress/.eslintrc.js: Environment key "cypress/globals" is unknown before it reads a file, on pristine main as well; eslint and prettier --check on the changed files are clean.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes if appropriate.
• All new and existing tests passed.