Past minute 30 of the wall clock the next forecast hour is closer to
utc_now() than the current hour, so the picker would land on (e.g.)
19:00Z when the user is at 18:43Z. HRRR has 19:00Z, but the HRDPS
chain only seeds the *current* hour (18:00Z), so the dual-source map
showed an empty Canadian half whenever we crossed the half-hour mark.
Switch to "most-recent valid_time <= now", with a fallback to the
closest future when nothing on disk is yet at-or-before now (cold
start). Hoist the picker into a public function so it can be unit-
tested deterministically — anchoring the integration test on
DateTime.utc_now() truncated to the hour would have only verified the
new behavior past minute 30.
/weather-ca delegates to the same picker so the two maps agree on
"current."
Graham McIntire
b37692592b