Add Nix flake for mcrctl

Vendor dependencies and expose mcrctl binary via nix build.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/github.com/pelletier/go-toml/v2/unstable/kind.go

@@ -0,0 +1,83 @@
+package unstable
+
+import "fmt"
+
+// Kind represents the type of TOML structure contained in a given Node.
+type Kind int
+
+const (
+	// Invalid represents an invalid meta node.
+	Invalid Kind = iota
+	// Comment represents a comment meta node.
+	Comment
+	// Key represents a key meta node.
+	Key
+
+	// Table represents a top-level table.
+	Table
+	// ArrayTable represents a top-level array table.
+	ArrayTable
+	// KeyValue represents a top-level key value.
+	KeyValue
+
+	// Array represents an array container value.
+	Array
+	// InlineTable represents an inline table container value.
+	InlineTable
+
+	// String represents a string value.
+	String
+	// Bool represents a boolean value.
+	Bool
+	// Float represents a floating point value.
+	Float
+	// Integer represents an integer value.
+	Integer
+	// LocalDate represents a a local date value.
+	LocalDate
+	// LocalTime represents a local time value.
+	LocalTime
+	// LocalDateTime represents a local date/time value.
+	LocalDateTime
+	// DateTime represents a data/time value.
+	DateTime
+)
+
+// String implementation of fmt.Stringer.
+func (k Kind) String() string {
+	switch k {
+	case Invalid:
+		return "Invalid"
+	case Comment:
+		return "Comment"
+	case Key:
+		return "Key"
+	case Table:
+		return "Table"
+	case ArrayTable:
+		return "ArrayTable"
+	case KeyValue:
+		return "KeyValue"
+	case Array:
+		return "Array"
+	case InlineTable:
+		return "InlineTable"
+	case String:
+		return "String"
+	case Bool:
+		return "Bool"
+	case Float:
+		return "Float"
+	case Integer:
+		return "Integer"
+	case LocalDate:
+		return "LocalDate"
+	case LocalTime:
+		return "LocalTime"
+	case LocalDateTime:
+		return "LocalDateTime"
+	case DateTime:
+		return "DateTime"
+	}
+	panic(fmt.Errorf("Kind.String() not implemented for '%d'", k))
+}