Fail Core lint when analyzers fail

[chubes4]

Summary

• Fail the WordPress core-dev lint runner when PHPCS, PHPStan, or JS lint fails instead of swallowing analyzer exits.
• Treat missing Core PHPCS/PHPStan binaries as infrastructure failures with a composer install hint.
• Prefer Core's phpcs.xml.dist while retaining .phpcs.xml.dist fallback, and add smoke coverage for success, analyzer failure, and missing PHPStan.

Motivation

This came out of reviewing why Homeboy did not flag a WordPress Core backport issue on WordPress/wordpress-develop#11766.

Weston Ruter noted a strict PHPStan foreach.nonIterable issue in src/wp-admin/site-editor.php: WordPress/wordpress-develop#11766 (comment)

Strict PHPStan did catch the issue when run directly, but Homeboy still reported success because the core-dev lint runner swallowed analyzer exits with || true. The runner also skipped PHPCS in Core because it looked for .phpcs.xml.dist while Core uses phpcs.xml.dist, and it treated missing Composer-installed analyzer binaries as warnings instead of actionable infrastructure failures.

Testing

• bash wordpress/scripts/test/core-dev-shape-smoke.sh
• bash -n wordpress/scripts/lint/lint-runner-core-dev.sh && bash -n wordpress/scripts/test/core-dev-shape-smoke.sh

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: Investigated the missed WordPress Core PHPStan coverage, drafted the shell runner fix and smoke coverage, and ran targeted validation. Chris remains responsible for review and merge.