refactor: use idiomatic hyperscript selector syntax

Replace verbose document.getElementById() and document.querySelectorAll()
with cleaner hyperscript syntax:
- #id for ID selectors
- .class and the first .class for class selectors
- <selector/> query literals for complex selectors
- #{variable} for dynamic ID interpolation

Files changed:
- utils._hs: scrollHeight, details, footer buttons, scrollToSection
- zoom._hs: all zoom control element selectors (14 changes)
- pdf-modal._hs: modal selector
- keyboard._hs: dynamic toggle and modal selectors
- contact-modal.html: response div and modal close
- index.html: ninja-keys bar selector

static/hyperscript/zoom._hs

@@ -11,7 +11,7 @@ def handleZoomInput(slider)
   set zoomLevel to zoomValue / 100
 
   -- Update display
-  set valueEl to document.getElementById('zoom-value-current')
+  set valueEl to #zoom-value-current
   if valueEl is not null
     put zoomValue into valueEl
   end
@@ -19,7 +19,7 @@ def handleZoomInput(slider)
   set slider's @aria-valuetext to `${zoomValue}%`
 
   -- Toggle reset button class
-  set resetBtn to document.getElementById('zoom-reset')
+  set resetBtn to #zoom-reset
   if resetBtn is not null
     if zoomValue is not 100
       add .zoom-not-default to resetBtn
@@ -29,7 +29,7 @@ def handleZoomInput(slider)
   end
 
   -- Apply zoom to wrapper
-  set wrapper to document.getElementById('zoom-wrapper')
+  set wrapper to #zoom-wrapper
   if wrapper is not null
     set wrapper's *zoom to zoomLevel
     -- Handle width for zoom > 100%
@@ -53,7 +53,7 @@ end
 -- ==============================================================================
 -- Called from reset button to reset zoom to 100%
 def handleZoomReset()
-  set slider to document.getElementById('zoom-slider')
+  set slider to #zoom-slider
   if slider is not null
     set slider.value to 100
     call handleZoomInput(slider)
@@ -73,7 +73,7 @@ def initZoomControl(control)
 
   -- Load saved zoom level
   set savedZoom to localStorage.getItem('cv-zoom')
-  set slider to document.getElementById('zoom-slider')
+  set slider to #zoom-slider
   if savedZoom and slider
     set slider.value to savedZoom
     call handleZoomInput(slider)
@@ -83,7 +83,7 @@ def initZoomControl(control)
   set isVisible to localStorage.getItem('cv-zoom-visible')
   if isVisible is 'true'
     remove .zoom-hidden from control
-    set menuBtn to document.getElementById('show-zoom-menu-btn')
+    set menuBtn to #show-zoom-menu-btn
     if menuBtn is not null
       add .zoom-hidden to menuBtn
     end
@@ -104,8 +104,8 @@ end
 -- ==============================================================================
 -- Show zoom control
 def showZoomControl()
-  set control to document.getElementById('zoom-control')
-  set menuBtn to document.getElementById('show-zoom-menu-btn')
+  set control to #zoom-control
+  set menuBtn to #show-zoom-menu-btn
   if control is not null
     remove .zoom-hidden from control
     set localStorage['cv-zoom-visible'] to 'true'
@@ -117,8 +117,8 @@ end
 
 -- Hide zoom control
 def hideZoomControl()
-  set control to document.getElementById('zoom-control')
-  set menuBtn to document.getElementById('show-zoom-menu-btn')
+  set control to #zoom-control
+  set menuBtn to #show-zoom-menu-btn
   if control is not null
     add .zoom-hidden to control
     set localStorage['cv-zoom-visible'] to 'false'
@@ -130,7 +130,7 @@ end
 
 -- Toggle zoom control visibility
 def toggleZoomControl()
-  set control to document.getElementById('zoom-control')
+  set control to #zoom-control
   if control is not null
     if control.classList.contains('zoom-hidden')
       call showZoomControl()