refactor: Add error wrapping with %w where appropriate

- Updated operator registration in rpn/operations.go:
  - registerStandardOperator now wraps handler errors with operator name context
  - registerCommandOperator now wraps handler errors with operator name context
  - registerHyperOperator now wraps handler errors with operator name context

- Updated Parse() in calculator/calculator.go:
  - Now wraps registry.parse() errors with context about the input
  - Returns a more descriptive error when parsing fails

All tests pass and the binary builds and runs correctly.

2 files changed, 5 insertions, 5 deletions

diff --git a/internal/calculator/calculator.go b/internal/calculator/calculator.go
index f953df7..0212279 100644
--- a/internal/calculator/calculator.go
+++ b/internal/calculator/calculator.go
@@ -97,10 +97,10 @@ func Parse(input string) (string, error) {
 		return calc.Format(), nil
 	}
 	if err != nil {
-		return "", err
+		return "", fmt.Errorf("calculator: unable to parse input %q: %w", input, err)
 	}
 
-	return "", fmt.Errorf("calculator: unable to parse input %q. See usage for examples", input)
+	return "", fmt.Errorf("calculator: unable to parse input %q: unknown error", input)
 }
 
 // ParseCalculation parses a percentage calculation input string and returns the Calculation object.
diff --git a/internal/rpn/operations.go b/internal/rpn/operations.go
index d749720..aeccf68 100644
--- a/internal/rpn/operations.go
+++ b/internal/rpn/operations.go
@@ -136,7 +136,7 @@ func NewOperatorRegistry(op Operator) *OperatorRegistry {
 func (r *OperatorRegistry) registerStandardOperator(name string, handler func(*Stack) error) {
 	r.standardOperators[name] = func(stack *Stack) (string, bool, error) {
 		if err := handler(stack); err != nil {
-			return "", false, err
+			return "", false, fmt.Errorf("%s: %w", name, err)
 		}
 		return "", true, nil
 	}
@@ -147,7 +147,7 @@ func (r *OperatorRegistry) registerCommandOperator(name string, handler func(*St
 	r.standardOperators[name] = func(stack *Stack) (string, bool, error) {
 		result, err := handler(stack)
 		if err != nil {
-			return "", false, err
+			return "", false, fmt.Errorf("%s: %w", name, err)
 		}
 		return result, true, nil
 	}
@@ -157,7 +157,7 @@ func (r *OperatorRegistry) registerCommandOperator(name string, handler func(*St
 func (r *OperatorRegistry) registerHyperOperator(name string, handler func(*Stack) error) {
 	r.hyperOperators[name] = func(stack *Stack) (string, bool, error) {
 		if err := handler(stack); err != nil {
-			return "", false, err
+			return "", false, fmt.Errorf("%s: %w", name, err)
 		}
 		return "", true, nil
 	}