CLN v26.06 deprecates getroute in favor of askrene's getroutes.
Replace the Dowser's getroute+listchannels loop (up to ~40 RPC
round-trips) with a single getroutes call and let askrene's
min-cost-flow solver enumerate multi-path capacity directly. Response
parsing follows the getroutes schema; 205/206 (no route / too
expensive) maps to zero capacity.
Size the probe to the caller's threshold. The Dowser is a flow
estimator: callers compare the dowsed flow against a channel size (the
janitor and preinvestigator min-channel acceptance test, the channel
creator's sizing). A fixed probe amount caps the estimate, so any
threshold at or above that cap rejects every candidate regardless of
real capacity. RequestDowser now carries a min_amount; callers that
test against a channel size set it, and the probe runs at
min_amount / reserve_factor so a full-flow result clears the threshold
for any configured channel size. The channel creator dowses at
max-channel so new channels size toward the operator ceiling instead
of being pinned at the min-channel floor. The manual clboss-dowser
command keeps the fixed default probe.
