Add CLAUDE.md documentation and update local settings to include directory listing CLI commands

Author: machibuse

.claude/settings.local.json

@@ -4,7 +4,8 @@
       "Bash(dotnet build:*)",
       "Bash(dotnet test:*)",
       "Bash(taskkill:*)",
-      "Bash(del \"D:\\\\GitHub\\\\Porticle.Grpc.TypeMapper\\\\Source\\\\Porticle.Grpc.TypeMapper\\\\bin\\\\Debug\\\\net9.0\\\\Porticle.Grpc.TypeMapper.dll\")"
+      "Bash(del \"D:\\\\GitHub\\\\Porticle.Grpc.TypeMapper\\\\Source\\\\Porticle.Grpc.TypeMapper\\\\bin\\\\Debug\\\\net9.0\\\\Porticle.Grpc.TypeMapper.dll\")",
+      "Bash(dir:*)"
     ]
   }
 }

CLAUDE.md

@@ -0,0 +1,48 @@
+# CLAUDE.md
+
+## Project Overview
+
+Porticle.Grpc.TypeMapper is a Roslyn-based post-processor shipped as a NuGet development dependency. It hooks into the build pipeline after `Protobuf_Compile` and rewrites protoc-generated C# classes to add support for Guids, nullable strings, and nullable enums — features not natively supported by Protocol Buffers.
+
+Proto field comments (`[GrpcGuid]`, `[NullableString]`, `[NullableEnum]`) or global project properties control which transformations are applied.
+
+## Solution Structure
+
+```
+Source/
+  Porticle.Grpc.sln
+  Porticle.Grpc.TypeMapper/     # Main library (NuGet package, net8.0 + net9.0)
+  Porticle.Grpc.UnitTests/      # MSTest unit tests (net9.0)
+  Porticle.Grpc.Test/            # Integration test with proto files
+  Porticle.Grpc.TestWithoutProto/ # Package consumption test without proto compilation
+```
+
+## Key Source Files
+
+| File | Role |
+|------|------|
+| `ProtoPostProcessor.cs` | MSBuild Task entry point — finds generated files, runs visitors, writes output |
+| `ClassVisitor.cs` | CSharpSyntaxRewriter — orchestrates property and method transformations per class |
+| `PropertyVisitor.cs` | Rewrites property types/getters/setters (Guid, nullable string, nullable enum) |
+| `MethodVisitor.cs` | Updates Equals/GetHashCode/WriteTo/MergeFrom etc. to use backing fields |
+| `PropertyToFieldRewriter.cs` | Replaces property identifiers with field names inside method bodies |
+| `ListWrappers.cs` | Source code strings for `RepeatedFieldGuidWrapper` and `IListWithRangeAdd<T>` |
+| `SyntaxHelper.cs` | Static helpers to parse C# source strings into Roslyn syntax nodes |
+| `StringUtils.cs` | Snake_case to CamelCase conversion matching protoc/gRPC naming conventions |
+| `Extensions.cs` | Small helper extensions (CheckNotNull, GetGetter, GetSetter) |
+| `Porticle.Grpc.TypeMapper.targets` | MSBuild targets file shipped in the NuGet package |
+
+## Build & Test
+
+```bash
+dotnet build Source/Porticle.Grpc.sln
+dotnet test Source/Porticle.Grpc.UnitTests
+```
+
+## Coding Conventions
+
+- All code comments (including XML doc comments) must be written in **English**.
+- Target frameworks: net8.0 and net9.0.
+- Nullable reference types are enabled (`<Nullable>enable</Nullable>`).
+- Implicit usings are enabled.
+- Debug builds treat warnings as errors.