chore(proto): add buf config for codegen and lint

Relaxes STANDARD lint rules that conflict with the terse service
shape from ARCHITECTURE.md §7.2 (shared Empty, no Service suffix).

buf.yaml

@@ -0,0 +1,15 @@
+version: v2
+modules:
+  - path: proto
+lint:
+  use:
+    - STANDARD
+  except:
+    - PACKAGE_DIRECTORY_MATCH
+    - SERVICE_SUFFIX
+    - RPC_REQUEST_STANDARD_NAME
+    - RPC_RESPONSE_STANDARD_NAME
+    - RPC_REQUEST_RESPONSE_UNIQUE
+breaking:
+  use:
+    - FILE