Collapse the five contributor tests from #101345 into two: one for the
error class (unloadable IANA name, non-string value) and one for the
silent class (valid, blank, missing, None, and no tz database at all).
Same coverage, half the surface — the salvage bar is two invariant tests
per fix.
Docs: the `timezone` section now says `hermes doctor` reports a value the
runtime cannot load, so users know where the typo surfaces.
teknium1
5f20bb8b63