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/go/README.md

@@ -3,7 +3,7 @@
 The Go client module contains the generated MXAccess Gateway protobuf bindings,
 a small handwritten `mxgateway` package, and the `mxgw-go` test CLI scaffold.
 The module 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
@@ -28,7 +28,7 @@ Run generation after the shared `.proto` files or the Go output path changes:
 ./generate-proto.ps1
 ```
 
-The script uses the tool paths recorded in `../../docs/toolchain-links.md`.
+The script uses the tool paths recorded in `../../docs/ToolchainLinks.md`.
 
 ## Build And Test
 
@@ -209,5 +209,5 @@ go run ./cmd/mxgw-go smoke -endpoint $env:MXGATEWAY_ENDPOINT -plaintext -api-key
 ## Related Documentation
 
 - [Client Packaging](../../docs/ClientPackaging.md)
-- [Client Proto Generation](../../docs/client-proto-generation.md)
-- [Go Client Detailed Design](../../docs/clients-golang-design.md)
+- [Client Proto Generation](../../docs/ClientProtoGeneration.md)
+- [Go Client Detailed Design](./GoClientDesign.md)