The Python passive check (`banner.check_for_updates`, used by the CLI
banner, `hermes --tui`, every `tui_gateway` spawn and the dashboard's
/api/hermes/update/check) also ran `git fetch origin main` on every cache
miss, and never cached an inconclusive result so a flaky line retried on
every start. Same GitHub complaint, same fix:
- remote tip via GET /repos/{slug}/commits/main (vnd.github.sha), local tip
via rev-parse, exact count + changelog via the compare API when they
differ. HTTPS `ls-remote` remains only as the fallback when the API is
unreachable or the origin isn't on GitHub.
- cache TTL 6h -> 24h, failures cached 1h; the cache is keyed on HEAD so
`hermes update` invalidates it immediately.
- the dashboard's "what's changed" list comes from the memoized compare
payload (`upstream_commits_behind`) instead of `git log HEAD..origin/main`,
which was stale without a fetch.
Tests rewritten to the new contract: passive checks must not run
`git fetch`/`ls-remote` for a GitHub origin; the daily cache invalidates
when HEAD moves and re-asks after the failure window.
338bf9ea9a