The sprout-agent → buzz-agent rename (d99ad131f) moved the OAuth cache
directory without migrating existing tokens. Users on the latest main
get a browser auth prompt on every agent spawn because the new path is
empty.
When the primary cache path has no token, check the equivalent path
under ~/.config/sprout-agent/oauth/ and copy it to the new location.
The copy makes the migration one-time; subsequent starts find the token
at the primary path.
Co-authored-by: Will Pfleger <wpfleger@block.xyz>
Signed-off-by: Will Pfleger <wpfleger@block.xyz>