ensureModeScript() used document.body.appendChild() to load lazy mode
scripts, but the preload for ?mode= query params runs in <head> before
<body> exists, causing all deep-linked modes to silently fail.
Also fix cross-mode handoffs (BT→BT Locate, WiFi→WiFi Locate,
Spy Stations→Waterfall) that assumed target module was already loaded.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
