Root cause of the blank /map analysis breakdown: the skippy.w5isp.com
caching proxy was unreachable from the cluster, so every f00 analysis
step failed at the idx fetch and Rust never wrote a ProfilesFile. The
/map point-detail panel silently degraded to empty factors because
no profile ever lands on `/data/scores/profiles/`.
HrrrClient now takes an optional fallback base. When the primary base
exhausts its retries (5× exponential backoff), fetches retry once
against the fallback — defaulted to the NOAA S3 public bucket. Forecast,
analysis, and native-duct paths all go through the same
fetch_blob_with_fallback helper so a proxy outage degrades to direct
S3 instead of stalling.
Moved the native-URL builder out of native_duct into fetcher so the
single helper can build both primary and fallback URLs for the native
hybrid-sigma product.