Query: Add unit test for redirect_guess_404_permalink() post_type array leak

[irozum]

What this adds: a new data-provider case for Tests_Canonical::test_redirect_guess_404_permalink_post_types() in tests/phpunit/tests/canonical.php, covering redirect_guess_404_permalink() in src/wp-includes/canonical.php.

Function under test: redirect_guess_404_permalink(), specifically the branch that builds the SQL post_type IN (...) clause when post_type is queried as an array (src/wp-includes/canonical.php, around line 985-989).

Case covered and why: a mix of one publicly viewable post type (page) and one non-viewable post type (wp_tests_private) in the post_type array, where a post of the non-viewable type matches the requested name prefix. Before the fix landed in trunk (efa21b21dd, ticket #44964), this branch built the SQL IN (...) clause from the raw, unfiltered get_query_var( 'post_type' ) array instead of the $post_types list already intersected against publicly viewable types two lines above — so a private/non-viewable post could be found and its permalink leaked as the guessed 404 redirect target, even though it should never have been considered. The existing data set already covered a single private post type (which short-circuits via the empty( $post_types ) guard before ever reaching the vulnerable SQL line) and a single public type, but nothing exercised the mixed-array path where the bug actually lived. I verified this test fails against the pre-fix code (reverting the one-line fix locally reproduces the leak and turns this exact case red) and passes against current trunk.

This is test-only — it adds no production behaviour. git diff trunk for this branch touches only tests/phpunit/tests/canonical.php.

Trac ticket: https://core.trac.wordpress.org/ticket/44964

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Sonnet 5
Used for: Surveying Trac for a coverage candidate, verifying the fix had landed in trunk and no test existed for it, drafting the test case and data-provider entry, and running the red/green verification loop (breaking the fix locally to confirm the new test fails, then reverting). I reviewed the diff, ticket, and test output before submitting.

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