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>

docs/Contracts.md

@@ -41,7 +41,7 @@ hand-edit generated files.
 Client generation inputs are published through
 `clients/proto/proto-inputs.json` and the descriptor set under
 `clients/proto/descriptors/`. See
-[Client Proto Generation](./client-proto-generation.md) for language-specific
+[Client Proto Generation](./ClientProtoGeneration.md) for language-specific
 generation inputs, output directories, and golden protobuf JSON fixtures.
 
 ## Generation
@@ -73,7 +73,7 @@ powershell -ExecutionPolicy Bypass -File scripts/publish-client-proto-inputs.ps1
 
 ## Related Documentation
 
-- [Client Proto Generation](./client-proto-generation.md)
-- [Gateway Process Detailed Design](./gateway-process-design.md)
-- [MXAccess Worker Instance Detailed Design](./mxaccess-worker-instance-design.md)
+- [Client Proto Generation](./ClientProtoGeneration.md)
+- [Gateway Process Detailed Design](./GatewayProcessDesign.md)
+- [MXAccess Worker Instance Detailed Design](./MxAccessWorkerInstanceDesign.md)
 - [Protobuf Style Guide](./style-guides/ProtobufStyleGuide.md)