Real-world telemetry showed --lang "English (United States)" failing
for several consumer products that only list "English International"
-- the exact example used in --help. The mismatch error now lists the
languages actually available, and the help text notes names vary by
product.
Also fixes truncateError to keep both head and tail of long error
strings (previously kept only the head, which for wrapped errors with
a long URL cut off the actual root cause at the end).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
