Add client behavior fixtures

docs/client-proto-generation.md

@@ -16,6 +16,7 @@ records:
 - the public and worker source files,
 - the descriptor set path,
 - golden fixture locations,
+- behavior fixture locations,
 - generated-code output directories for each planned client.
 
 The source files listed by the manifest are:
@@ -125,9 +126,30 @@ The fixtures use protobuf JSON field names and enum values. Contract tests parse
 them with the generated C# types so schema drift is caught before client
 generation work starts.
 
+## Behavior Fixtures
+
+Cross-language behavior fixtures live in
+`clients/proto/fixtures/behavior`. The manifest
+`clients/proto/fixtures/behavior/manifest.json` lists command replies, ordered
+event stream samples, value conversion cases, status conversion cases, auth
+error expectations, and timeout/cancel expectations.
+
+The behavior fixtures let each generated client wrapper test the same
+expectations without a live gateway. Protobuf message fixtures parse with the
+generated types. Auth and timeout/cancel files describe wrapper behavior above
+the generated transport layer, including credential redaction and the rule that
+client cancellation does not abort an in-flight MXAccess COM call.
+
+Run the focused validation script after changing these fixtures:
+
+```powershell
+scripts/validate-client-behavior-fixtures.ps1
+```
+
 ## Related Documentation
 
 - [Protobuf Contracts](./Contracts.md)
 - [Client Libraries Detailed Design](./client-libraries-design.md)
+- [Client Behavior Fixtures](./ClientBehaviorFixtures.md)
 - [Client Libraries Implementation Plan](./implementation-plan-clients.md)
 - [Protobuf Style Guide](./style-guides/ProtobufStyleGuide.md)