2.9.0rc3: feature enhancements and bug fixes

What's Changed

• [2.9] Surface source helper types before conversion probes by @chesterxgchen in #5225
• Remove SkillEvaluator direct dependency from package metadata by @IsaacYangSLA in #5227
• [Auto-FL] Clarify literature review depth by @holgerroth in #5229
• NVSkills CI integration validation by @chesterxgchen in #5084
• Draft FLARE 2.9.0 release notes [skip-ci] by @chesterxgchen in #5085
• Remove DiLoCo from the roadmap by @chesterxgchen in #5235
• Correct Slurm internal connection security in design doc by @pcnudde in #5236
• Document Slurm shared-file worker transport by @pcnudde in #5237
• Fix StatisticsController._validate_min_clients returning True when no clients responded by @cch0 in #5230
• Remove simple_logging from Collab by @nvidianz in #5238
• Add Collaboration API and Agent Skills guides by @chesterxgchen in #5231
• Improve external process timeout diagnostics by @YuanTingHsieh in #5228

New Contributors

• @cch0 made their first contribution in #5230

Full Changelog: 2.9.0rc2...2.9.0rc3