refactor: Major hyperscript refactoring and JS elimination

Inline Hyperscript Refactoring:
- Body tag keyboard handlers: 20→8 lines (using helper functions)
- Zoom control handlers: 85→35 lines (using zoom._hs)
- PDF modal card selection: 90→6 lines (3 identical blocks eliminated)

New Hyperscript Files:
- zoom._hs: handleZoomInput, handleZoomReset, initZoomControl
- pdf-modal._hs: selectPdfCard, handlePdfCardKey

JavaScript Elimination (232 lines removed):
- cv-functions.js: REMOVED - hyperscript defs are globally available
- scroll-at-bottom-handler.js: REMOVED - duplicate of handleScroll()
- footer-buttons-interaction.js: REMOVED - moved to hyperscript

Added Tests:
- 32-hyperscript-multi-src.test.mjs: Verifies multi-file loading
- 33-keyboard-shortcuts-refactored.test.mjs: Keyboard shortcuts
- 34-hyperscript-refactor-comprehensive.test.mjs: Full test suite

Key Findings:
- No hyperscript multi-file bug in 0.9.14
- Hyperscript def statements are globally accessible
- Previous refactoring failures were syntax errors, not library bugs

static/hyperscript/utils._hs

@@ -134,6 +134,21 @@ def handleScroll()
   set :lastScroll to currentScroll
 end
 
+-- ==============================================================================
+-- FOOTER HOVER INTERACTION
+-- ==============================================================================
+-- 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')
+  for btn in buttons
+    if show
+      add .footer-hovered to btn
+    else
+      remove .footer-hovered from btn
+    end
+  end
+end
+
 -- ==============================================================================
 -- KEYBOARD SHORTCUTS
 -- ==============================================================================