internal/rpn/variables: Reorder types and functions per Go best practices

- Moved VariableInfo type to top of file, before Variables type
- NewVariables constructor now immediately follows type definitions
- This aligns with project Go best practices for file organization

1 files changed, 6 insertions, 6 deletions

diff --git a/internal/rpn/variables.go b/internal/rpn/variables.go
index 40f0844..69f5b18 100644
--- a/internal/rpn/variables.go
+++ b/internal/rpn/variables.go
@@ -68,6 +68,12 @@ func (s *Stack) Clear() {
 	s.values = s.values[:0]
 }
 
+// VariableInfo represents a single variable with its name and value.
+type VariableInfo struct {
+	Name  string
+	Value float64
+}
+
 // Variables stores variable name-value pairs for RPN calculations.
 // It provides thread-safe access to variable storage.
 type Variables struct {
@@ -149,12 +155,6 @@ func (v *Variables) ListVariables() []VariableInfo {
 	return infos
 }
 
-// VariableInfo represents a single variable with its name and value.
-type VariableInfo struct {
-	Name  string
-	Value float64
-}
-
 // ClearVariables removes all variables from storage.
 // Usage: `clear` removes all variables.
 func (v *Variables) ClearVariables() {