Fix "Expression is always true" errors

[glen-84]

Summary of the changes (Less than 80 chars)

• Fix "Expression is always true" errors.

[Copilot]

Pull request overview

This PR addresses “Expression is always true” warnings by removing redundant null checks and adding targeted analyzer suppressions where runtime nullability differs from the declared API contract.

Changes:

• Removed redundant null checks and simplified assertions that are always true under current nullability contracts.
• Added ReSharper suppressions for nullable-flow warnings that can’t be expressed cleanly with current type annotations.
• Simplified root type resolution in the execution pipeline.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Mocha/src/Mocha/Runtime/MessagingRuntimeHostedService.cs	Removes redundant null-check before disposing the hosted runtime.
src/HotChocolate/Utilities/src/Utilities.Buffers/ChunkedArrayWriter.cs	Adds suppression around chunk null-check in drain/cleanup loop.
src/HotChocolate/Fusion/src/Fusion.Execution/Transport/Http/FileEntryBuilder.cs	Simplifies path handling by removing redundant parent null checks.
src/HotChocolate/Data/src/Data/Projections/Expressions/Handlers/QueryableProjectionScalarHandler.cs	Adds suppression for nullable-flow loop condition during expression unwrapping.
src/HotChocolate/Core/test/Types.Tests/Types/Relay/NodeTypeTests.cs	Simplifies “no errors” assertion assuming Errors is non-null.
src/HotChocolate/Core/test/Types.Tests/Types/Relay/NodeResolverTests.cs	Simplifies “no errors” assertion assuming Errors is non-null.
src/HotChocolate/Core/test/Types.Tests/Types/ObjectTypeTests.cs	Adds suppression for context non-null check in async resolver test helper.
src/HotChocolate/Core/test/Types.CursorPagination.Tests/UseConnectionAttributeTests.cs	Simplifies “no errors” assertion assuming Errors is non-null.
src/HotChocolate/Core/src/Types/Execution/Pipeline/OperationExecutionMiddleware.cs	Removes query root null-guard and resolves query root directly from schema.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (2c9fa85) to head (08db6a7).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@     Coverage Diff      @@
##   main   #9517   +/-   ##
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