Add integration coverage for lightweight roots with args and generics

[NikolayPianikov]

Motivation

• Provide comprehensive integration coverage for the extended RootKinds.Light behavior to ensure lightweight roots support root arguments and generic type parameters and their combinations.
• Capture behavior across positive and negative scenarios, including tagged/named arguments, multiple arguments, nested generics, generic constraints, static/exposed roots, and different visibility modifiers.

Description

• Replaced/expanded the test file tests/Pure.DI.IntegrationTests/LightweightRootsTests.cs with ~32 xUnit tests covering lightweight roots with single/multiple root arguments, named and tagged args, and max-arity (Func<...> limits).
• Added generic scenarios: single and multiple generic parameters, nested generics, and generic constraints (class, struct, new()), plus combinations of generics with root arguments and different marker types (TT, TT1, TT2, TT3).
• Added edge-case tests for Static | Light, Exposed | Light, and visibility combinations (Public, Internal, Private, Protected) as well as negative tests that assert compilation/runtime failures for wrong argument types, missing arguments, and violated generic constraints.
• Tests follow the existing pattern using [Fact], RunAsync(), Options for language/version control, and Given/When/Then comments, and assert both result.Success and result.StdOut where applicable.

Testing

• Attempted to run the integration test suite locally with dotnet test, but the command failed in this environment because the dotnet runtime is not available (execution error: bash: command not found: dotnet).
• No automated test execution was completed in this environment; the new tests are constructed to run under CI or a local environment with the .NET SDK and will exercise compilation and runtime behavior via RunAsync() when executed.

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Codex Task