Update golangci-lint configuration to v2

[TerryHowe]

% golangci-lint version
golangci-lint has version 2.5.0 built with go1.25.1 from ff63786c on 2025-09-21T19:04:05Z

The run:

% golangci-lint run ./...
WARN [linters_context] copyloopvar: this linter is disabled because the Go version (1.18) of your project is lower than Go 1.22 
WARN [linters_context] intrange: this linter is disabled because the Go version (1.18) of your project is lower than Go 1.22 
0 issues.