refactor: use hyperscript event filtering and destructuring

- Use event filtering [key is 'Enter' or key is ' '] on PDF modal cards
- Remove handlePdfCardKey helper function (now inline)
- Use event destructuring on keydown(key, target, ctrlKey, metaKey, altKey)
- Cleaner, more idiomatic hyperscript patterns

static/hyperscript/pdf-modal._hs

@@ -33,13 +33,3 @@ def selectPdfCard(card)
   set window.selectedPdfFormat to card's @data-cv-format
 end
 
--- ==============================================================================
--- PDF CARD KEYDOWN HANDLER
--- ==============================================================================
--- Handles keyboard navigation for PDF cards (Enter/Space to select)
-def handlePdfCardKey(card, evt)
-  if evt.key is 'Enter' or evt.key is ' '
-    call evt.preventDefault()
-    call selectPdfCard(card)
-  end
-end