bring the repo up to repo standards (closes #1)

Adopt the standard tooling from sneak/prompts: the Makefile and script/
entrypoints, lint and test stages in one Dockerfile, the lint config, the
CI workflow and the formatter settings. make fmt also formats Go, with a
pinned Go from script/bootstrap. The module path becomes
sneak.berlin/go/dcf.

Fix the lint findings in pkg/dcf. DCFStore becomes Store and DCFObject
becomes Object. Three behaviours change. An error listing mount points is
now returned, where a typo used to drop it. Store.String() prints Store{
instead of DCFStore{, and a negative total as 0 B instead of a huge size.

Replace the placeholder test with real tests. Move the README into the
required sections. make build compiles the library; it pointed at a
command that does not exist.

Model: opus-5-5
Co-authored-by: clawbot <sneak+clawbot@sneak.cloud>

go.mod

@@ -1,6 +1,6 @@
-module git.eeqj.de/sneak/dcf
+module sneak.berlin/go/dcf
 
-go 1.22.1
+go 1.26.2
 
 require (
 	github.com/dustin/go-humanize v1.0.1
@@ -9,7 +9,6 @@ require (
 
 require (
 	github.com/go-ole/go-ole v1.3.0 // indirect
-	github.com/lmittmann/tint v1.0.4 // indirect
 	github.com/yusufpapurcu/wmi v1.2.4 // indirect
 	golang.org/x/sys v0.20.0 // indirect
 )