refactor(rpn): move dead Value type to test file

Value struct and its methods (NewNumberValue, NewBoolValue, IsBool,
IsNumber, Bool, Float64, Number, String) are defined in number.go but
never called in production code — only used in number_value_test.go.

Move the Value type and all its methods into the test file so they
don't pollute the production package.

2 files changed, 74 insertions, 71 deletions

diff --git a/internal/rpn/number.go b/internal/rpn/number.go
index 5e27dae..a188edf 100644
--- a/internal/rpn/number.go
+++ b/internal/rpn/number.go
@@ -407,75 +407,4 @@ func (s *Symbol) IsBool() bool    { return false }
 func (s *Symbol) IsString() bool  { return false }
 func (s *Symbol) Metric() *Metric { return GetCoolMetric() }
 
-// Value represents a variant type that can hold either a number (float64) or a boolean.
-//
-// When used in arithmetic operations, boolean values are automatically coerced:
-//   - true -> 1
-//   - false -> 0
-//
-// This allows boolean results from comparison operations to be used directly in
-// arithmetic expressions (e.g., "5 3 == 1 +" where "5 3 ==" produces false=0,
-// and "0 + 1" produces 1).
-type Value struct {
-	isBool  bool
-	boolVal bool
-	numVal  float64
-}
-
-// NewNumberValue creates a new Value containing a float64 number.
-func NewNumberValue(n float64) Value {
-	return Value{isBool: false, numVal: n}
-}
-
-// NewBoolValue creates a new Value containing a boolean.
-func NewBoolValue(b bool) Value {
-	return Value{isBool: true, boolVal: b}
-}
-
-// IsBool returns true if the value is a boolean.
-func (v Value) IsBool() bool {
-	return v.isBool
-}
-
-// IsNumber returns true if the value is a number.
-func (v Value) IsNumber() bool {
-	return !v.isBool
-}
-
-// Bool returns the boolean value, or false if the value is not a boolean.
-func (v Value) Bool() bool {
-	return v.boolVal
-}
 
-// Float64 returns the float64 value.
-// If the value is a boolean, true returns 1 and false returns 0.
-// If the value is a number, it returns the numeric value directly.
-func (v Value) Float64() float64 {
-	if v.isBool {
-		if v.boolVal {
-			return 1
-		}
-		return 0
-	}
-	return v.numVal
-}
-
-// Number returns the float64 value.
-// If the value is a boolean, this returns 0 (the numeric value is not used for booleans).
-// Deprecated: Use Float64 instead.
-func (v Value) Number() float64 {
-	return v.numVal
-}
-
-// String returns the string representation of the value.
-// For booleans, it returns "true" or "false".
-// For numbers, it returns the formatted float64 value.
-func (v Value) String() string {
-	if v.isBool {
-		if v.boolVal {
-			return "true"
-		}
-		return "false"
-	}
-	return fmt.Sprintf("%.10g", v.numVal)
-}
diff --git a/internal/rpn/number_value_test.go b/internal/rpn/number_value_test.go
index 51385bb..8f43ab7 100644
--- a/internal/rpn/number_value_test.go
+++ b/internal/rpn/number_value_test.go
@@ -4,10 +4,84 @@
 package rpn
 
 import (
+	"fmt"
 	"math/big"
 	"testing"
 )
 
+// Value represents a variant type that can hold either a number (float64) or a boolean.
+//
+// When used in arithmetic operations, boolean values are automatically coerced:
+//   - true -> 1
+//   - false -> 0
+//
+// This allows boolean results from comparison operations to be used directly in
+// arithmetic expressions (e.g., "5 3 == 1 +" where "5 3 ==" produces false=0,
+// and "0 + 1" produces 1).
+type Value struct {
+	isBool  bool
+	boolVal bool
+	numVal  float64
+}
+
+// NewNumberValue creates a new Value containing a float64 number.
+func NewNumberValue(n float64) Value {
+	return Value{isBool: false, numVal: n}
+}
+
+// NewBoolValue creates a new Value containing a boolean.
+func NewBoolValue(b bool) Value {
+	return Value{isBool: true, boolVal: b}
+}
+
+// IsBool returns true if the value is a boolean.
+func (v Value) IsBool() bool {
+	return v.isBool
+}
+
+// IsNumber returns true if the value is a number.
+func (v Value) IsNumber() bool {
+	return !v.isBool
+}
+
+// Bool returns the boolean value, or false if the value is not a boolean.
+func (v Value) Bool() bool {
+	return v.boolVal
+}
+
+// Float64 returns the float64 value.
+// If the value is a boolean, true returns 1 and false returns 0.
+// If the value is a number, it returns the numeric value directly.
+func (v Value) Float64() float64 {
+	if v.isBool {
+		if v.boolVal {
+			return 1
+		}
+		return 0
+	}
+	return v.numVal
+}
+
+// Number returns the float64 value.
+// If the value is a boolean, this returns 0 (the numeric value is not used for booleans).
+// Deprecated: Use Float64 instead.
+func (v Value) Number() float64 {
+	return v.numVal
+}
+
+// String returns the string representation of the value.
+// For booleans, it returns "true" or "false".
+// For numbers, it returns the formatted float64 value.
+func (v Value) String() string {
+	if v.isBool {
+		if v.boolVal {
+			return "true"
+		}
+		return "false"
+	}
+	return fmt.Sprintf("%.10g", v.numVal)
+}
+
 func TestNewNumberValue(t *testing.T) {
 	v := NewNumberValue(42.5)
 	if !v.IsNumber() {