register_status_widget(): pure Python wrapper that adds a live widget
to the main window status bar with context menu discoverability.
Origin query bindings (kcsdk.list_origins, active_origin, get_origin,
set_active_origin): thin C++ forwarding to OriginManager with Python
wrappers using kcsdk-first routing.
IOriginProvider and IStatusBarProvider C++ interfaces dropped — existing
FileOrigin stack is already complete, and status bar widgets don't need
C++ lifecycle management.
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