fix: use loop variable instead of global ticker in GenerateFreshName

The function used a global `ticker` variable but never incremented it
inside the loop, causing an infinite loop if the first generated name
was already in the used set.

This fix removes the global state and uses the loop variable `i`
directly, which is cleaner and avoids the bug.

pkg/lambda/generate_name.go

@@ -6,13 +6,11 @@ import (
 	"git.maximhutz.com/max/lambda/pkg/set"
 )
 
-var ticker uint64 = 0
-
 // GenerateFreshName generates a variable name that is not in the used set.
 // This function does not mutate the used set.
 func GenerateFreshName(used set.Set[string]) string {
 	for i := uint64(0); ; i++ {
-		attempt := "_" + string(strconv.AppendUint(nil, ticker, 10))
+		attempt := "_" + string(strconv.AppendUint(nil, i, 10))
 
 		if !used.Has(attempt) {
 			return attempt