v4.4.0 — the pin moves to Go 1.27.1

Go 1.27.1 is the pin; go.mod says go 1.27. The 1.27 rulings: httptest.NewTestServer for handler tests and inside a synctest bubble, synctest.Sleep, header limits at their defaults, Close drains (drainAndClose gone), uuid as a stdlib row, errors.AsType the rule with errors.As the named exception, encoding/json/v2 not adopted. htmx 4.0.0 is stable since 2026-08-28 and stays banned until adopted deliberately. Reference v4.4.0 (4d1ea3f) pins ce86f13: verify.sh 79 gates, exit 0; make ci green under go1.27.1. Sixty-nine review findings over sixteen passes, the last two clean.