ci: publish .NET test results on pull requests

[ReubenBond]

GitHub Actions currently archives the MTP-generated TRX files, but GitHub does not ingest test result artifacts into pull request checks. Test outcomes therefore remain visible only inside the workflow artifacts.

This adds a workflow_run reporter for completed .NET CI pull request runs. It reads the existing test_output_* artifacts and creates per-job check runs with result counts, failed test details, and annotations.

The reporter runs from the default branch with narrowly scoped actions: read and checks: write permissions. This preserves read-only CI execution for fork pull requests while allowing the trusted reporting workflow to publish their results. The action is pinned to the v3.0.0 commit.

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

Adds a dedicated GitHub Actions workflow which publishes .NET CI TRX test results directly into PR checks (via per-job check runs), so reviewers no longer need to download workflow artifacts to see failures.

Changes:

• Introduces a new workflow_run-triggered workflow which runs on completed .NET CI PR runs and reads existing test_output_* artifacts.
• Uses a pinned dorny/test-reporter action (v3.0.0 commit) to generate check runs with failed suite/test details and up to 50 annotations.
• Applies narrowly scoped permissions (actions: read, checks: write, contents: read) suitable for reporting from the default branch.

Show a summary per file

File	Description
.github/workflows/test-results.yml	New reporter workflow to publish TRX results from .NET CI artifacts into PR checks.

Review details

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• Review effort level: Lite