ci: publish Azure Pipelines code coverage

[ReubenBond]

Azure DevOps test runs currently produce test results without publishing coverage, leaving the Code Coverage tab empty.

This change collects a distinct Cobertura report from every suite/framework test job, preserves those reports as pipeline artifacts, and publishes their aggregate through PublishCodeCoverageResults@2. Azure and GitHub share the same coverage setup, collection scripts, and configuration.

Coverage retains normal ContinuousIntegrationBuild semantics. Deterministic reports preserve /_/ source paths while the existing source filters keep measurement scoped to repository code under src/.

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

Adds end-to-end code coverage publication for Azure Pipelines test runs by reusing the existing GitHub Actions coverage scripts/config, producing per-suite/per-framework Cobertura reports, preserving them as pipeline artifacts, and publishing the aggregated result via PublishCodeCoverageResults@2 so the Azure DevOps Code Coverage tab is populated.

Changes:

• Collect coverage in each Azure Pipelines test job via setup-coverage.ps1 + invoke-coverage.ps1, outputting distinct coverage-{suite}-{framework}.cobertura.xml reports to job artifacts.
• Add a dedicated Azure Pipelines job to download all Cobertura artifacts and publish aggregated coverage results (failing if empty).
• Align CI semantics and report determinism across GitHub and Azure by preserving ContinuousIntegrationBuild behavior and enabling deterministic reports in shared coverage configs.

Show a summary per file

File	Description
.github/scripts/test-summarize-coverage.ps1	Extends CI validation to assert Azure Pipelines coverage collection/version pinning and deterministic coverage configuration.
.github/scripts/setup-coverage.ps1	Supports non-GitHub CI by allowing an explicit tool install path and only appending to GITHUB_PATH when present.
.github/coverage.static.config.xml	Enables deterministic report paths and adjusts assembly-without-sources handling for static instrumentation.
.github/coverage.config.xml	Enables deterministic report paths and adjusts assembly-without-sources handling for dynamic instrumentation.
.github/actions/dotnet-test/action.yml	Removes forced ContinuousIntegrationBuild=false so GitHub coverage retains normal CI build semantics.
.azure/pipelines/templates/vars.yaml	Pins DOTNET_COVERAGE_VERSION for Azure Pipelines to match GitHub’s coverage tool versioning approach.
.azure/pipelines/templates/build.yaml	Collects and archives Cobertura per test job, then downloads and publishes aggregated coverage via PublishCodeCoverageResults@2.

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• Files reviewed: 7/7 changed files
• Comments generated: 0
• Review effort level: Lite