Clarify some aspects of dotnet run -

[jjonescz]

Tests and docs only change.

[Copilot]

Pull request overview

This PR adds test coverage and documentation for the dotnet run - feature (reading C# code from standard input). The changes clarify important behavioral aspects, specifically that the current working directory is used for building/executing even though it's not used to search for other files, and that $(MSBuildStartupDirectory) can be used to reference projects relative to the working directory.

• Added test coverage verifying working directory behavior for dotnet run -
• Added tests demonstrating that Directory.Build.props doesn't affect stdin-based runs (must use #:property directive instead)
• Added tests showing project references work with $(MSBuildStartupDirectory) but not with simple relative paths
• Enhanced documentation to explain working directory behavior and MSBuildStartupDirectory usage pattern

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
test/dotnet.Tests/CommandTests/Run/RunFileTests.cs	Enhanced ReadFromStdin test to verify working directory and added two new tests (ReadFromStdin_BuildProps and ReadFromStdin_ProjectReference) to validate Directory.Build.props isolation and project reference behavior
documentation/general/dotnet-run-file.md	Added clarification that working directory is still used for building/executing stdin programs and documented the $(MSBuildStartupDirectory) pattern for project references