Add self-validation to integration tests

[Copilot]

Integration tests now run SonarMark's built-in self-validation suite and capture TRX results for each OS/runtime combination.

Changes

• New step: Run SonarMark self-validation - Executes sonarmark --validate --results integration-test-${{ matrix.os }}-dotnet${{ matrix.dotnet-version }}.trx to generate test results and report pass/fail to console
• New step: Upload integration test results - Uploads TRX files as artifacts named integration-test-results-${{ matrix.os }}-dotnet${{ matrix.dotnet-version }} with if: always() to capture results even on failure

Self-validation tests verify quality gate status retrieval, issues retrieval, hot-spots retrieval, and markdown report generation using mock data.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[Feature]: Run Self-Validation</issue_title>
<issue_description>### Problem Statement

The integration tests should include running the SonarMark self-validation and saving the test results

Proposed Solution

Modify the integration-test job of build.yaml to include two extra steps:

1. Run the SonarMark self-validation to generate integration-test-${{ matrix.os }}-dotnet${{ matrix.dotnet-version }}.trx and to report the pass/fail to the console
2. Upload the TRX results file to an artifact called integration-test-results-${{ matrix.os }}-dotnet${{ matrix.dotnet-version }}

Alternatives Considered

No response

Additional Context

No response

Priority

High - Blocking current work

Contribution

• I would be willing to submit a PR for this feature

Code of Conduct

• I agree to follow this project's Code of Conduct</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Feature]: Run Self-Validation #35

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