Support float for `:dur`

```clojure
(play :sine :a5 {:dur 1})  ; int supported
;; => {:voice 0 :generation 2 :instrument :sine :id 4 :start-frame 10971136 :note 81 :epoch 2 :start-beat 124389297/250000}

(play :sine :a5 {:dur 0.1})  ; float unsupported

error: beat overflow
  --> <default>:1:1
   |
 1 | (play :sine :a5 {:dur 0.1})
   | ^^^

stack trace:
  at play (<default>:1:1)
```