Add Windows integration tests showing that subst is handled inconsistently

[jketema]

This shows that we do not consistently handle this across the CLI and the various extractors. All tests are: extract a file, check if the extracted file is relative to the source root, where the source root is a subst drive.

[Copilot]

Pull request overview

Adds new Windows-only integration tests across multiple language packs to demonstrate inconsistent handling of subst-mapped source roots when extracting files and evaluating whether file paths are treated as relative to the source root.

Changes:

• Introduce new subst integration-test directories for Rust, Ruby, Python, JavaScript, Go, Java/Kotlin, and C#.
• For each test: create a database with source_root on a subst drive, then run a small query and compare .expected results to show (in)consistencies.
• Add minimal source files per language to drive extraction on Windows.

Show a summary per file

File	Description
rust/ql/integration-tests/subst/test.py	Windows integration test that creates a Rust DB with a subst-drive source root.
rust/ql/integration-tests/subst/file.ql	Query selecting files and whether a relative path exists (test oracle).
rust/ql/integration-tests/subst/file.expected	Expected results for Rust extraction under subst.
rust/ql/integration-tests/subst/code/test.rs	Minimal Rust source for extraction.
ruby/ql/integration-tests/subst/test.py	Windows integration test that creates a Ruby DB with a subst-drive source root.
ruby/ql/integration-tests/subst/file.ql	Query selecting files and whether a relative path exists (test oracle).
ruby/ql/integration-tests/subst/file.expected	Expected results for Ruby extraction under subst.
ruby/ql/integration-tests/subst/code/test.rb	Minimal Ruby source for extraction.
python/ql/integration-tests/subst/test.py	Windows integration test that creates a Python DB with a subst-drive source root.
python/ql/integration-tests/subst/file.ql	Query selecting files and whether a relative path exists (test oracle).
python/ql/integration-tests/subst/file.expected	Expected results for Python extraction under subst.
python/ql/integration-tests/subst/code/main.py	Minimal Python source for extraction.
javascript/ql/integration-tests/subst/test.py	Windows integration test that creates a JavaScript DB with a subst-drive source root.
javascript/ql/integration-tests/subst/file.ql	Query selecting files and whether a relative path exists (test oracle).
javascript/ql/integration-tests/subst/file.expected	Expected results for JavaScript extraction under subst.
javascript/ql/integration-tests/subst/code/test.ts	Minimal TypeScript source for extraction.
javascript/ql/integration-tests/subst/code/main.js	Minimal JavaScript source for extraction.
java/ql/integration-tests/java/subst/test.py	Windows integration test that creates a Java/Kotlin DB with a subst-drive source root.
java/ql/integration-tests/java/subst/file.ql	Query selecting files and whether a relative path exists (test oracle).
java/ql/integration-tests/java/subst/file.expected	Expected results for Java/Kotlin extraction under subst.
java/ql/integration-tests/java/subst/code/test2.kt	Minimal Kotlin source for extraction.
java/ql/integration-tests/java/subst/code/test1.java	Minimal Java source for extraction.
go/ql/integration-tests/subst/test.py	Windows integration test that creates a Go DB with a subst-drive source root.
go/ql/integration-tests/subst/file.ql	Query selecting files and whether a relative path exists (test oracle).
go/ql/integration-tests/subst/file.expected	Expected results for Go extraction under subst.
go/ql/integration-tests/subst/code/main.go	Minimal Go source for extraction.
csharp/ql/integration-tests/windows/subst/test.py	Windows integration test that creates a C# DB with a subst-drive source root.
csharp/ql/integration-tests/windows/subst/file.ql	Query selecting files and whether a relative path exists (test oracle).
csharp/ql/integration-tests/windows/subst/file.expected	Expected results for C# extraction under subst.
csharp/ql/integration-tests/windows/subst/code/Program.cs	Minimal C# program used for extraction/build.
csharp/ql/integration-tests/windows/subst/code/global.json	.NET SDK pin for the test project.
csharp/ql/integration-tests/windows/subst/code/dotnet_build.csproj	Minimal .NET project configuration for extraction/build.

Review details

• Files reviewed: 32/32 changed files
• Comments generated: 1
• Review effort level: Low