Move the CLI to urfave/cli v3 (closes #110)

Ported per the library's v2-to-v3 migration guide: the app is a root
cli.Command, actions take a context and the command, and flag environment
variables become value sources. -v, -q and the version flag are marked
local so that, as before, only the commands that define them accept them.
ErrWriter is stdout so usage errors print with their help, as before.
go mod tidy raises testify to v1.12.1, which v3 requires. The
urfave_cli_no_docs build tag is dropped; v3 has no such tag. v3 no longer
refuses a flag given under two of its names, so -v --verbose now gives
debug output, and the test that pinned the refusal becomes a
TestVerboseCount case. Help text follows v3's templates.

Model: opus-5-5

internal/cli/entry_test.go

@@ -18,7 +18,7 @@ import (
 	"github.com/spf13/afero"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	urfcli "github.com/urfave/cli/v2"
+	urfcli "github.com/urfave/cli/v3"
 	"sneak.berlin/go/mfer/internal/log"
 	"sneak.berlin/go/mfer/mfer"
 )
@@ -264,8 +264,9 @@ func commandsTakingVerbose() [][]string {
 }
 
 // TestVerboseCount asserts that one -v or --verbose gives verbose output and
-// two -v give debug output (issue #125). urfave/cli before v2.25.5 counted a
-// flag given by its alias twice, so one -v gave debug output.
+// two -v, or -v and --verbose, give debug output (issue #125). urfave/cli
+// before v2.25.5 counted a flag given by its alias twice, so one -v gave debug
+// output.
 func TestVerboseCount(t *testing.T) {
 	t.Parallel()
 
@@ -276,6 +277,7 @@ func TestVerboseCount(t *testing.T) {
 		{[]string{"-v"}, log.VerboseLevel},
 		{[]string{testFlagVerbose}, log.VerboseLevel},
 		{[]string{"-v", "-v"}, log.DebugLevel},
+		{[]string{"-v", testFlagVerbose}, log.DebugLevel},
 	}
 
 	for _, command := range commandsTakingVerbose() {
@@ -313,28 +315,6 @@ func TestCombinedShortVerboseRefused(t *testing.T) {
 	}
 }
 
-// TestShortAndLongVerboseRefused asserts that -v and --verbose given together
-// are refused (issue #125): urfave/cli v2 refuses a flag given under two of its
-// names, and one flag with an alias keeps help and parsing simple.
-func TestShortAndLongVerboseRefused(t *testing.T) {
-	t.Parallel()
-
-	for _, command := range commandsTakingVerbose() {
-		args := slices.Concat(command, []string{"-v", testFlagVerbose})
-
-		t.Run(strings.Join(args, " "), func(t *testing.T) {
-			t.Parallel()
-
-			opts := testOpts(args, afero.NewMemMapFs())
-			exitCode, level := runCLIWithLevel(opts)
-
-			assert.Equal(t, 1, exitCode)
-			assert.Contains(t, testStderr(t, opts), "Cannot use two forms of the same flag")
-			assert.Equal(t, log.InfoLevel, level)
-		})
-	}
-}
-
 func TestHelpCommand(t *testing.T) {
 	t.Parallel()