test(review): Needs review page workflows

The review fixture now seeds a real monitor-fallback conflict (the
monitor pipeline links a new output to the most recent prompt, then
queues it), a limited item and a file under no current root, and can add
an output through the monitor or leave one for a metadata scan.

New workflows: Apply links the chosen pair to that file only; a real
association conflict leaves the links unchanged and explains; a limited
item and an unavailable file can only be left unresolved; a tag save
leaves the item pending; keyboard focus, labels and touch targets; an
open page shows items the monitor and a scan add and a decision made in
another tab; leaving the page releases captures, the change stream and
requests. The faked 409 conflict test is replaced by the real one.

tests/browser/server.py

@@ -582,6 +582,8 @@ def create_app(root: Path) -> web.Application:
         api.db.close_all()
 
     seed()
+    # Open Needs review change streams end first, as on the real host.
+    app.on_shutdown.append(api.close_review_events)
     app.on_cleanup.append(cleanup)
     app.add_routes(routes)
     return app