Add directory class diagram scanning

[HandyS11]

This pull request introduces support for recursive directory scanning for class diagram generation in ProjGraph. Users can now generate a combined Mermaid class diagram for all classes in a directory, with automatic exclusion of standard folders and a warning for large sets. The update is thoroughly documented and includes new sample outputs, specification artifacts, and improvements to the sample regeneration script.

Feature: Directory Scanning for Class Diagrams

• Added recursive directory scanning for .cs files, enabling generation of a single combined class diagram for all types in a directory. Standard folders like .git, bin, obj, and node_modules are automatically excluded, and a warning is issued if more than 50 files are found. [1] [2] [3]
• CLI and documentation updated to show usage: projgraph classdiagram ./Models/ generates a combined diagram for all classes in the directory. [1] [2]
• New sample output file simple-hierarchy-folder.mmd demonstrates directory scan results.

Specification and Planning Artifacts

• Added specification checklist, contract, data model, and implementation plan for the directory scanning feature, ensuring requirements are clear and testable. [1] [2] [3] [4]

Sample Regeneration Script Improvements

• Updated regenerate-samples.ps1 to support directory scanning and output parameter, simplifying file writing and adding a new sample for directory scan. [1] [2]

Technology References

• Updated technology references and recent changes to include Roslyn for directory scanning and memory analysis. [1] [2]

Sample Cleanup

• Removed trailing blank lines from sample diagram files for consistency. [1] [2] [3] [4] [5] [6] [7]

[Copilot]

Pull request overview

This pull request adds recursive directory scanning support to the class diagram generation feature in ProjGraph. Users can now provide a directory path instead of a single .cs file to generate a combined Mermaid class diagram of all types found in that directory and its subdirectories. The implementation automatically excludes standard artifact folders (bin, obj, .git, node_modules), creates a single Roslyn compilation for cross-file analysis, and warns users when scanning more than 50 files.

Changes:

• Added directory scanning infrastructure with DiscoverCsFilesUseCase and AnalyzeDirectoryUseCase
• Extended IClassAnalysisService with AnalyzeDirectoryAsync method
• Updated CLI and MCP server to accept directory paths in addition to file paths
• Added comprehensive test coverage including unit, integration, and contract tests
• Created detailed specification artifacts and updated documentation

Reviewed changes

Copilot reviewed 45 out of 45 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/ProjGraph.Lib.Core/Abstractions/IFileSystem.cs	Added DirectoryExists, GetDirectories, and GetFiles methods to support directory traversal
src/ProjGraph.Lib.Core/Infrastructure/PhysicalFileSystem.cs	Implemented new IFileSystem methods with proper documentation
src/ProjGraph.Lib.Core/Infrastructure/DirectoryFilters.cs	Refactored to expose constants (Bin, Obj, Git, NodeModules, CSharpExtension) for reuse
src/ProjGraph.Lib.Core/Infrastructure/WorkspaceRootResolver.cs	Updated to use DirectoryFilters.Git constant
src/ProjGraph.Lib.ClassDiagram/Application/UseCases/DiscoverCsFilesUseCase.cs	New use case implementing recursive directory scanning with exclusion logic
src/ProjGraph.Lib.ClassDiagram/Application/UseCases/AnalyzeDirectoryUseCase.cs	New use case orchestrating multi-file analysis with unified Roslyn compilation
src/ProjGraph.Lib.ClassDiagram/Application/IClassAnalysisService.cs	Added AnalyzeDirectoryAsync method signature
src/ProjGraph.Lib.ClassDiagram/Application/ClassAnalysisService.cs	Implemented directory analysis delegation
src/ProjGraph.Lib.ClassDiagram/DependencyInjection.cs	Registered new use cases in DI container
src/ProjGraph.Lib.ClassDiagram/Rendering/MermaidClassDiagramRenderer.cs	Minor refactoring of AppendLine usage
src/ProjGraph.Cli/Commands/ClassDiagramCommand.cs	Updated validation and execution to handle both files and directories with 50-file warning
src/ProjGraph.Mcp/Program.cs	Updated GetClassDiagramAsync to support directories with warning markup for large sets
tests/ProjGraph.Tests.Unit.ClassDiagram/DiscoverCsFilesUseCaseTests.cs	Unit tests for directory discovery logic
tests/ProjGraph.Tests.Unit.ClassDiagram/AnalyzeDirectoryUseCaseTests.cs	Unit tests for directory analysis including edge cases
tests/ProjGraph.Tests.Integration.Cli/ClassDiagramCommandTests.cs	Integration tests for CLI directory scanning
tests/ProjGraph.Tests.Integration.Mcp/McpClassDiagramTests.cs	Integration test for MCP directory scanning
tests/ProjGraph.Tests.Contract/McpClassDiagramTests.cs	Updated contract test to verify "directory" in description
samples/regenerate-samples.ps1	Updated to use --output parameter instead of capturing stdout
samples/classdiagram/simple-hierarchy/simple-hierarchy-folder.mmd	New sample output demonstrating directory scan
specs/009-directory-class-diagram/*	Complete specification artifacts (spec, plan, research, tasks, contracts, checklist)
Documentation files	Updated README, CLI README, MCP README, ARCHITECTURE.md with directory scanning examples

Comments suppressed due to low confidence (1)

tests/ProjGraph.Tests.Integration.Mcp/McpClassDiagramTests.cs:270

• The test method name GetClassDiagram_WithDepth1_ShouldLimitRelationshipDepth suggests it explicitly tests depth=1, but the test now relies on the default MaxDepth value (which happens to be 1). Consider either explicitly passing MaxDepth: 1 to make the test intention clear, or renaming the test to GetClassDiagram_WithDefaultDepth_ShouldLimitRelationshipDepth to accurately reflect what is being tested.

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