27: Assert which mistake was reported, not that one was

[nikolaystrikhar]

What: Tests\Support\Traits\WithIncorrectUsage records the reported message and offers an assertion that matches it; LoaderTest and Boot\SchedulerTest use it, and the late-boot fallback gains an ordering assertion.

Usage:

$this->assert_the_library_reported_incorrect_usage_saying(
    'The registered sub-plugins could not be read, so no conflict was resolved',
    'The duplicate slug is what stood the conflict pass down.'
);

Why this way:

"A report happened" is not an assertion about the cause. Four Loader cases and both resolve_conflicts() catch arms passed on a report from anything at all — deleting the Config_Exception arm outright left the suite green.

The recorder already existed, privately, in one file. It moves to the trait rather than being copied, since the loose assertion still suits callers that only need it.

expect_incorrect_usage() was leaking listeners. run_halted_request() calls it, so two halted requests in one scenario stranded a listener bound to a finished test object on doing_it_wrong_run for the rest of the process.

The inline fallback was asserted for the load and not the conflict step, so a fallback iterating only the last element of sequence() passed everything — the case where losing conflict resolution means both copies load and the request fatals.