docs(cli): clarify adapter organization

.changeset/calm-tools-explain.md

@@ -0,0 +1,5 @@
+---
+"@perfect-abstractions/compose-cli": patch
+---
+
+Clarify CLI adapter and adapter test organization in the contributor documentation.

website/docs/contribution/cli/code-style-guide.mdx

@@ -194,6 +194,7 @@ Use an adapter when a module needs to call an external tool, framework, library,
 - A pipeline should resolve adapter dependencies explicitly and pass them into the module.
 - Feature logic and validation should be handled in modules.
 - External communication and library-specific details should be handled in adapters.
+- Organize adapters by interface. Keep the interface and every implementation of that contract in the same `I<AdapterName>/` directory.
 - For stable dependencies that are unlikely to change often, such as basic CLI parsing or filesystem access, a module helper, module, or util may be more practical than adding an adapter.
 
 Example:

website/docs/contribution/cli/testing.mdx

@@ -13,7 +13,7 @@ Tests follow the same boundaries as the implementation: module behavior is teste
 
 ## Test Structure
 
-The `cli/test` directory mirrors `cli/src`. Keep each feature's test, harness, and fixtures together.
+The `cli/test` directory mirrors `cli/src`. Keep each feature's test, harness, and fixtures together. Organize adapter tests by interface, with the tests, harnesses, and fixtures for a contract under the same `I<AdapterName>/` directory.
 
 ```text
 cli/test/