fix: use loop variable instead of global ticker in GenerateFreshName (#40)

## Description

`GenerateFreshName` used a global `ticker` variable but never incremented it inside the loop.
This caused an infinite loop if the first generated name (`_0`) was already in the used set.

- Remove global `ticker` variable.
- Use loop variable `i` directly to generate candidate names.

## Benefits

- Fixes infinite loop bug when generated name collides with used set.
- Removes unnecessary global state.
- Simpler and more predictable behavior.

## Checklist

- [x] Code follows conventional commit format.
- [x] Branch follows naming convention (`<type>/<description>`). Always use underscores.
- [x] Tests pass (if applicable).
- [x] Documentation updated (if applicable).

Reviewed-on: #40
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>

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