Can string/keyword harvesting be parameterized?

Any chance these can be parameterized?

```clojure
; girouette.processor:88-95
(defn- string->classes [s]
(->> (str/split s #"\s+")
(remove str/blank?)))

(defn- kw->classes [kw]
(->> (name kw)
(re-seq #"\.[^\.#]+")
(map (fn [s] (subs s 1)))))
```

I'd prefer to use keywords over strings for conditional classes (e.g `:class (if something [:class-1 :class-2] [:class-3])`). Not a deal breaker, this project is awesome! But this would make it that much _more_ awesome, I think.

Start with girouette.processor lines 88-95, especially string->classes and kw->classes, and trace how class values are harvested. Work out how parameterization should support conditional keyword class vectors while preserving existing string and keyword behavior. Review the surrounding processor code to identify the relevant verification path and confirm both input forms still produce the expected classes.

Written by the indexing model from the issue text.