ci: Update Magefile to include shortcuts for build, test, lint, and release

- Added Lint target: runs golangci-lint for code quality checks
- Added Release target: builds and packages releases (requires goreleaser)

Also fixed errcheck linting issue:
- Check error return from o.vars.SetVariable in AssignVariable

All mage targets work: build, run, test, testRPN, rpn, install, lint, release, repl, uninstall

1 files changed, 1 insertions, 2 deletions

diff --git a/internal/rpn/operations.go b/internal/rpn/operations.go
index 3bd0fc1..d9965ed 100644
--- a/internal/rpn/operations.go
+++ b/internal/rpn/operations.go
@@ -711,8 +711,7 @@ func (o *Operations) AssignVariable(stack *Stack, name string) error {
 	}
 
 	// Convert Value to float64 for variable storage
-	o.vars.SetVariable(name, toNumber(val))
-	return nil
+	return o.vars.SetVariable(name, toNumber(val))
 }
 
 // UseVariable pushes a variable's value onto the stack.