feat(cmd): implement fetch and status commands, update deps to go1.26.1

- Implement fetch command: fetches all registered repos without merging,
  supports parallel execution via -j/--jobs flag
- Implement status command: shows uncommitted changes across all repos
  with per-file-type counts, supports parallel execution
- Update Go to 1.26.1
- Update go-git v5.16.5 -> v5.17.0, go-crypto v1.3.0 -> v1.4.0,
  go-billy v5.7.0 -> v5.8.0, x/net v0.50.0 -> v0.51.0
- Fix unregister command description (said 'add' instead of 'remove')
- Fix goimports formatting in mgconf_test.go

parse/mgconf_test.go

@@ -51,8 +51,8 @@ func TestExpandPaths(t *testing.T) {
 			expected: []string{"/absolute/path/to/repo"},
 		},
 		{
-			name: "empty repos",
-			input: []Repo{},
+			name:     "empty repos",
+			input:    []Repo{},
 			expected: []string{},
 		},
 		{
@@ -138,8 +138,8 @@ func TestCollapsePaths(t *testing.T) {
 			},
 		},
 		{
-			name: "empty repos",
-			input: []Repo{},
+			name:     "empty repos",
+			input:    []Repo{},
 			expected: []string{},
 		},
 		{
@@ -328,12 +328,12 @@ func TestParseMGConfig(t *testing.T) {
 
 func TestAddRepo(t *testing.T) {
 	tests := []struct {
-		name       string
-		initial    []Repo
-		addPath    string
-		addRemote  string
-		wantErr    bool
-		wantCount  int
+		name      string
+		initial   []Repo
+		addPath   string
+		addRemote string
+		wantErr   bool
+		wantCount int
 	}{
 		{
 			name:      "add to empty",