Media-control emoji (U+23EE U+23F8 U+23F9 U+23ED) and 🔊 🔇 📋 🚫
are absent from the iOS 9 system font and render as empty boxes on iPad 2.

Added isLegacyIOS detection (iOS <= 9 via UA) and a SYM symbol table
that picks between emoji (modern) and plain-text fallbacks for iOS 9:
  prev=<< pause=|| stop=■ next=>> volOn=vol volOff=mut playlist=PL skip=✕

Static buttons replaced at boot; dynamic updates (play/pause, mute)
use SYM throughout. Modern browsers completely unaffected.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>