refactor: update module docstrings for clarity and consistency

backend/app/schemas/gateway_api.py

@@ -1,15 +1,21 @@
+"""Schemas for gateway passthrough API request and response payloads."""
+
 from __future__ import annotations
 
 from sqlmodel import SQLModel
 
-from app.schemas.common import NonEmptyStr
+from app.schemas.common import NonEmptyStr  # noqa: TCH001
 
 
 class GatewaySessionMessageRequest(SQLModel):
+    """Request payload for sending a message into a gateway session."""
+
     content: NonEmptyStr
 
 
 class GatewayResolveQuery(SQLModel):
+    """Query parameters used to resolve which gateway to target."""
+
     board_id: str | None = None
     gateway_url: str | None = None
     gateway_token: str | None = None
@@ -17,6 +23,8 @@ class GatewayResolveQuery(SQLModel):
 
 
 class GatewaysStatusResponse(SQLModel):
+    """Aggregated gateway status response including session metadata."""
+
     connected: bool
     gateway_url: str
     sessions_count: int | None = None
@@ -28,20 +36,28 @@ class GatewaysStatusResponse(SQLModel):
 
 
 class GatewaySessionsResponse(SQLModel):
+    """Gateway sessions list response payload."""
+
     sessions: list[object]
     main_session_key: str | None = None
     main_session: object | None = None
 
 
 class GatewaySessionResponse(SQLModel):
+    """Single gateway session response payload."""
+
     session: object
 
 
 class GatewaySessionHistoryResponse(SQLModel):
+    """Gateway session history response payload."""
+
     history: list[object]
 
 
 class GatewayCommandsResponse(SQLModel):
+    """Gateway command catalog and protocol metadata."""
+
     protocol_version: int
     methods: list[str]
     events: list[str]