Ensures a feed's topology walk is at least under way, without waiting for
it. Index movement never holds the session's lane: a cold feed's walk is
started here and runs detached, deduped by the in-flight map, annunciated
by the load register, and committed to the cache when it lands (which
emits the feed's change event, the signal a watch answers).
Ensures a feed's topology walk is at least under way, without waiting for it. Index movement never holds the session's lane: a cold feed's walk is started here and runs detached, deduped by the in-flight map, annunciated by the load register, and committed to the cache when it lands (which emits the feed's change event, the signal a watch answers).