v4.3

goimports stopped reinstalling on every run because GOPATH paths are normalized before comparison, the registry PATH checks moved from wildcard pattern matching to exact array matching, and $GOPATH/bin is now added to the current session PATH unconditionally for immediate tool availability. Ruby left the bootstrap entirely, taking the bashcov gem, the ruby entries in the PowerShell and Bash version checks, and the ruby entry in packages.yaml, because coverage moved to kcov exclusively: native kcov on Linux and macOS, kcov through Docker on Windows. The README reflects the kcov-only strategy, drops gem from the supported language package managers, and shows kcov through Docker for Windows in the coverage tools table.