Align docs with StyleGuide and add CLAUDE.md

- Rename 16 kebab-case docs to PascalCase per StyleGuide
- Move per-language client design docs from docs/ to clients/<lang>/
  alongside their READMEs
- Add ## Related Documentation sections to 15 docs that lacked one
- Fix sentence-case violations in H3 headings (StyleGuide rule)
- Update cross-references in gateway.md, client READMEs, scripts,
  and generate-proto.ps1 helpers to follow the new paths
- Add CLAUDE.md with build/test commands, the source-update
  verification matrix, the parity-first contract, and pointers
  to MXAccess and Galaxy Repository analysis sources

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

clients/python/README.md

@@ -3,7 +3,7 @@
 The Python client package contains generated MXAccess Gateway protobuf
 bindings, the async `mxgateway` package, and the `mxgw-py` test CLI. The
 package uses the shared proto inputs documented in
-`../../docs/client-proto-generation.md` so gateway and client contracts stay in
+`../../docs/ClientProtoGeneration.md` so gateway and client contracts stay in
 sync.
 
 ## Layout
@@ -31,7 +31,7 @@ changes:
 ```
 
 The script uses the Python tool path recorded in
-`../../docs/toolchain-links.md`.
+`../../docs/ToolchainLinks.md`.
 
 ## Build And Test
 
@@ -219,5 +219,5 @@ mxgw-py smoke --endpoint $env:MXGATEWAY_ENDPOINT --plaintext --api-key-env MXGAT
 ## Related Documentation
 
 - [Client Packaging](../../docs/ClientPackaging.md)
-- [Client Proto Generation](../../docs/client-proto-generation.md)
-- [Python Client Detailed Design](../../docs/clients-python-design.md)
+- [Client Proto Generation](../../docs/ClientProtoGeneration.md)
+- [Python Client Detailed Design](./PythonClientDesign.md)