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 canonical lint
config, the CI workflow and the formatter settings. Change the module
path to sneak.berlin/go/dcf.

Fix the lint findings in pkg/dcf in place. DCFStore becomes Store and
DCFObject becomes Object. One behaviour changes: an error listing mount
points is now returned, where a typo used to drop it.

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

Model: opus-5-5

go.sum

@@ -3,8 +3,6 @@ github.com/dustin/go-humanize v1.0.1/go.mod h1:Mu1zIs6XwVuF/gI1OepvI0qD18qycQx+m
 github.com/go-ole/go-ole v1.2.6/go.mod h1:pprOEPIfldk/42T2oK7lQ4v4JSDwmV0As9GaiUsvbm0=
 github.com/go-ole/go-ole v1.3.0 h1:Dt6ye7+vXGIKZ7Xtk4s6/xVdGDQynvom7xCFEdWr6uE=
 github.com/go-ole/go-ole v1.3.0/go.mod h1:5LS6F96DhAwUc7C+1HLexzMXY1xGRSryjyPPKW6zv78=
-github.com/lmittmann/tint v1.0.4 h1:LeYihpJ9hyGvE0w+K2okPTGUdVLfng1+nDNVR4vWISc=
-github.com/lmittmann/tint v1.0.4/go.mod h1:HIS3gSy7qNwGCj+5oRjAutErFBl4BzdQP6cJZ0NfMwE=
 github.com/shirou/gopsutil v3.21.11+incompatible h1:+1+c1VGhc88SSonWP6foOcLhvnKlUeu/erjjvaPEYiI=
 github.com/shirou/gopsutil v3.21.11+incompatible/go.mod h1:5b4v6he4MtMOwMlS0TUMTu2PcXUg8+E1lC7eC3UO/RA=
 github.com/yusufpapurcu/wmi v1.2.4 h1:zFUKzehAFReQwLys1b/iSMl+JQGSCSjtVqQn9bBrPo0=