Standardize GitHub GraphQL type naming for consistency

[Copilot]

Pull Request

Description

GitHub GraphQL types had inconsistent naming: IssueNode (minimal) vs IssueNodeData (full) broke the pattern used by other node types (PullRequestNode, ReleaseNode, TagNode, CommitNode).

Changes:

• IssueNode → LinkedIssueReference - clarifies this represents a minimal reference (number only) to issues linked from pull requests
• IssueNodeData → IssueNode - standardizes as the primary issue node type with full data

Architecture preserved:
GitHubGraphQLClient continues returning raw GraphQL types; transformation to domain types (Info types) remains in GitHubRepoConnector. This separation of concerns is intentional.

No Octokit collisions found - codebase has no Octokit references.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code quality improvement

Related Issues

Pre-Submission Checklist

Before submitting this pull request, ensure you have completed the following:

Build and Test

• Code builds successfully: dotnet build --configuration Release
• All tests pass: dotnet test --configuration Release
• Code produces zero warnings

Code Quality

• Code formatting is correct: dotnet format --verify-no-changes
• New code has appropriate XML documentation comments
• Static analyzer warnings have been addressed

Quality Checks

Please run the following checks before submitting:

• Spell checker passes: cspell "**/*.{md,cs}"
• Markdown linter passes: markdownlint "**/*.md"
• YAML linter passes: yamllint '**/*.{yml,yaml}'

Testing

• Added unit tests for new functionality
• Updated existing tests if behavior changed
• All tests follow the AAA (Arrange, Act, Assert) pattern
• Test coverage is maintained or improved

Documentation

• Updated README.md (if applicable)
• Updated ARCHITECTURE.md (if applicable)
• Added code examples for new features (if applicable)
• Updated requirements.yaml (if applicable)

Additional Notes

All 70 GitHub-related tests pass. CodeQL reports 0 alerts.

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