Without SFDUPES_DATABASE, a user other than root now uses
sfdupes/db.sqlite under $XDG_STATE_HOME (~/.local/state by default),
which scan creates, instead of failing on /var/lib/sfdupes. Root keeps
/var/lib/sfdupes/db.sqlite. sfdupes --help and README say where the
database is. Adds github.com/adrg/xdg, the decided XDG library.
Model: opus-5-5
`go install sneak.berlin/go/sfdupes/cmd/sfdupes@...` found no package: the command was built from `package main` in the repository root. It now lives in `cmd/sfdupes/main.go`, whose one call is `sfdupes.Main()`, and every other Go file moved with `git mv` to `internal/sfdupes`, as `REPO_POLICIES.md` and the Go style guide require. The `Makefile` builds `./cmd/sfdupes` and sets `Version` by its new import path. README "Install" and `TODO.md` give the new paths; the fleet-written "flat layout" divergence is gone.
Rule suppressed: each test file carries `//nolint:testpackage`, since the tests call unexported functions throughout.
Model: opus-5-5