fix: filtered WP Codebox PHPUnit runs double-load test config

[chubes4]

Problem

Passing PHPUnit arguments through homeboy review test causes the WP Codebox PHPUnit worker to crash before executing tests, while the same project reaches PHPUnit without passthrough arguments.

Reproduction

From Extra-Chill/data-machine-events PR #530, Homeboy action run 30035017999 invoked:

homeboy review test --placement local data-machine-events --path ... --changed-since 2f99076 -- --filter \"VenueProfileMutationsTest|CheckMissingVenueAddressesCommandTest\"

The runner correctly selected the two files, then crashed during WordPress test installation:

Warning: Constant DB_NAME already defined in /tmp/wp-tests-config.php on line 3
Warning: Constant DB_USER already defined in /tmp/wp-tests-config.php on line 4
Warning: Constant DB_PASSWORD already defined in /tmp/wp-tests-config.php on line 5
Warning: Constant DB_HOST already defined in /tmp/wp-tests-config.php on line 6
Warning: Constant DB_CHARSET already defined in /tmp/wp-tests-config.php on line 7
Warning: Constant ABSPATH already defined in /tmp/wp-tests-config.php on line 12
Warning: Undefined variable $wpdb in .../wp-phpunit/includes/install.php on line 56

Job: https://github.com/Extra-Chill/data-machine-events/actions/runs/30035017999/job/89300698506

Expected

Filtered/file-scoped PHPUnit runs should use the same single-load managed bootstrap as full-suite runs and execute the selected tests.

Notes

• Homeboy CLI: 0.310.3
• WordPress extension revision: aee32285
• WP Codebox source SHA: 1edb4779
• The preceding standalone real-MySQL test step passed.
• A prior unfiltered run reached PHPUnit 9.6.35 and executed 634 tests, so this is specific to the filtered invocation path.

[chubes4]

Follow-up: run 30036177381 reproduced the same double-load crash after removing all explicit PHPUnit passthrough arguments. Homeboy changed-file selection still chose the venue test files automatically. This therefore appears to affect the current changed-file WP Codebox PHPUnit path generally, not only explicit --filter passthrough. The prior successful 634-test execution used WordPress extension revision f9f90fa; both current crashes use aee3228.