New Phase 0 in diagnose(): three generate_204-style probes run before every
other module, using detect-and-tag rather than short-circuit — a portal is
rarely total (DNS/ICMP often pass while only HTTP is intercepted), and an
aborted run would look identical to a dead link. On detection every later
phase still runs, tagged with a crit finding and a banner at the top of the
report.
Caught live before it shipped: detectportal.firefox.com/success.txt (one of
the original three default check URLs) returns 200 "success" on a genuinely
clean connection, which the generate_204-shaped classifier misread as a
portal redirect. Swapped for a second real generate_204 endpoint instead of
teaching the classifier a second success shape.
Also redesigned the speedtest server geo-sanity check after checking the
bundled Ookla CLI's actual JSON output: its server object never carries
lat/lon (documented schema, not a version gap), so speed.server_other_country
compares server_country against the client's own country instead of a
haversine distance that no tier can actually supply.
Part of plans/zesty-zooming-wilkinson.md (gitignored).
