Only bitcoincash: was being stripped; bchtest: (chipnet) addresses ended up
producing preferred_username="bch_bchtest:qzew3dqcsj0g" — Forgejo rejected
that with "name is invalid ... must be valid alpha or numeric or dash(-_)
or dot characters" because of the colon, callback 500'd, session never
finished. Regex-strip any [a-z]+: prefix so all three prefix families
(bitcoincash, bchtest, bchreg) produce clean usernames.
Verified end-to-end with a Node smoke test signing a real chipnet challenge
with the main wallet from Argus/wallets.json:
bchtest:qzew3dqcsj0guwe5y3uxf9q2xs5ajgy9lca4z093cu
→ bch_qzew3dqcsj0guwe5y3ux (auto-provisioned in Forgejo)
→ 303 to dashboard, session live.
11b7b5b85e