feat: allow extra context during board onboarding

backend/app/api/board_onboarding.py

@@ -180,6 +180,10 @@ async def start_onboarding(
         "- 1 question to choose a unique name for the board lead agent (first-name style).\n"
         "- 2-4 questions to capture the user's preferences for how the board lead should work\n"
         "  (communication style, autonomy, update cadence, and output formatting).\n"
+        '- Always include a final question: "Anything else we should know?" (constraints, context,\n'
+        '  preferences). Provide an option like "Yes (I\'ll type it)" so they can fill the free-text field.\n'
+        '- If the user sends an "Additional context" message later, incorporate it and resend status=complete\n'
+        "  to update the draft (until the user confirms).\n"
         "Do NOT respond in OpenClaw chat.\n"
         "All onboarding responses MUST be sent to Mission Control via API.\n"
         f"Mission Control base URL: {base_url}\n"

backend/app/core/error_handling.py

@@ -95,7 +95,9 @@ def _error_payload(*, detail: Any, request_id: str | None) -> dict[str, Any]:
     return payload
 
 
-async def _request_validation_handler(request: Request, exc: RequestValidationError) -> JSONResponse:
+async def _request_validation_handler(
+    request: Request, exc: RequestValidationError
+) -> JSONResponse:
     # `RequestValidationError` is expected user input; don't log at ERROR.
     request_id = _get_request_id(request)
     return JSONResponse(
@@ -104,7 +106,9 @@ async def _request_validation_handler(request: Request, exc: RequestValidationEr
     )
 
 
-async def _response_validation_handler(request: Request, exc: ResponseValidationError) -> JSONResponse:
+async def _response_validation_handler(
+    request: Request, exc: ResponseValidationError
+) -> JSONResponse:
     request_id = _get_request_id(request)
     logger.exception(
         "response_validation_error",