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/utils._hs

@@ -67,8 +67,8 @@ def handleScroll()
   set isMenuOpen to menu.classList.contains('menu-open')
 
   -- Calculate if at bottom (within 50px)
-  set scrollHeight to document.documentElement.scrollHeight
-  set clientHeight to document.documentElement.clientHeight
+  set scrollHeight to the document's documentElement's scrollHeight
+  set clientHeight to the document's documentElement's clientHeight
   set isAtBottom to (scrollHeight - currentScroll - clientHeight) < 50
 
   -- Reset keepHeaderVisible when scrolling up
@@ -144,7 +144,7 @@ end
 -- Expand all <details> elements in the CV
 def expandAllSections(evt)
   if evt then call evt.preventDefault() end
-  set details to document.querySelectorAll('details')
+  set details to <details/>
   for d in details
     set d's @open to ''
   end
@@ -153,7 +153,7 @@ end
 -- Collapse all <details> elements in the CV
 def collapseAllSections(evt)
   if evt then call evt.preventDefault() end
-  set details to document.querySelectorAll('details')
+  set details to <details/>
   for d in details
     call d.removeAttribute('open')
   end
@@ -164,7 +164,7 @@ end
 -- ==============================================================================
 -- Adds/removes footer-hovered class to fixed buttons when hovering footer
 def setFooterHover(show)
-  set buttons to document.querySelectorAll('.download-btn, .print-friendly-btn, .shortcuts-btn, .info-button, .back-to-top, .color-theme-switcher')
+  set buttons to <.download-btn, .print-friendly-btn, .shortcuts-btn, .info-button, .back-to-top, .color-theme-switcher/>
   for btn in buttons
     if show
       add .footer-hovered to btn
@@ -199,11 +199,11 @@ end
 -- Smooth scroll to a section by ID
 def scrollToSection(evt, sectionId)
   if evt then call evt.preventDefault() end
-  set el to document.getElementById(sectionId)
+  set el to #{sectionId}
   if el is not null
     call el.scrollIntoView({ behavior: 'smooth' })
     -- Close the menu after navigation
-    set menu to document.querySelector('.navigation-menu')
+    set menu to the first .navigation-menu
     if menu is not null
       remove .menu-hover from menu
       remove .menu-open from menu