A GitHub-side HTTP 429 during 'hermes update' printed only
'Failed to fetch updates from origin.' — and the curl
'unable to access ... returned error: 429' shape even matched the
network-error branch, blaming the user's connection for a GitHub
outage.
- new _classify_fetch_failure(): 429/rate-limit -> 'GitHub is rate
limiting requests or having an outage — try again in 5 minutes';
5xx -> outage message with githubstatus.com; ordered BEFORE the
generic 'unable to access' network check
- both fetch-failure sites (update apply + --check) now share the
classifier via _print_fetch_failure(), and both always print the
first raw stderr line so the wire error stays diagnosable
- tests: classifier matrix + E2E against a live local HTTP server
returning 429 through real git
Fixes#89287
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