fix: pass owner to start_research in chat stream path (#1265)

* fix: pass owner to start_research in chat stream path

Research launched from the chat stream omits the owner parameter,
causing those research sessions to never appear in the user's
research library (which filters by owner). All other start_research
call sites in this file already pass owner=_user.

* test: assert all start_research calls in chat_routes pass owner

Uses AST inspection to verify every start_research() call site
includes the owner= keyword argument, preventing regressions where
new call sites forget to scope research by user.

routes/chat_routes.py

@@ -711,6 +711,7 @@ def setup_chat_routes(
                         prior_findings=_prior_findings,
                         prior_urls=_prior_urls,
                         on_complete=_on_research_done,
+                        owner=_user,
                     )
 
                     _heartbeat_counter = 0