Re-enable MNG-1088 IT: concurrent builder correctly handles reactor plugins

[gnodet]

Summary

Re-enable MavenITmng1088ReactorPluginResolutionTest, which was disabled pending the concurrent builder work (MNG-7977).

Background

MNG-1088 covers the case where a plugin is built and used within the same multiproject build. In Maven 3, this worked via a fallback: if the plugin's JAR hadn't been produced yet, Maven would resolve it from the repository. This fallback was fragile and could cause inconsistencies (MNG-7977).

How the Concurrent Builder Fixes This

Maven 4's BuildPlanExecutor handles this correctly in computePlan():

// If a project declares a plugin that is itself part of the reactor,
// require the plugin project to reach 'ready' before planning the consumer
MavenProject pluginProject = reactorGavs.get(gav(plugin));
if (pluginProject != null) {
    plan.requiredStep(project, PLAN).executeAfter(plan.requiredStep(pluginProject, READY));
}

The ready phase sits after compile and resources, so the plugin's classes are compiled and packaged before the consuming project is planned and executed — regardless of which lifecycle phase the user requested on the command line.

Verification

IT passes against 4.0.0-SNAPSHOT:

Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
Time elapsed: 9.579 s -- in org.apache.maven.it.MavenITmng1088ReactorPluginResolutionTest
BUILD SUCCESS

The test description is updated to reflect the Maven 4 semantics (proper scheduling via the concurrent build plan, rather than fallback to repository resolution).

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Hermes Agent (Claude Sonnet 4.6) on behalf of Guillaume Nodet