Add ISE split orientation toggle (horizontal/vertical) #1432

Summary

Add the ability to toggle the ISE results splitter between horizontal (top/bottom) and vertical (left/right) orientation.

Features

• Status bar toggle button to switch between horizontal and vertical split
• Toggle icon updates to reflect current orientation (mirror_vertically / mirror_horizontally)
• Draggable splitter in both orientations with CSS grip dot indicators
• Hover and active states on splitter bars for visual feedback
• Splitter position and orientation persisted in localStorage (spe::ise.splitOrientation, spe::ise.splitPosition)
• Double-click splitter to reset to 50/50
• Minimum pane size of 100px enforced to prevent collapse
• Show/hide results works in both orientations
• Tooltips on splitter and toggle button
• Feature added to ISE tips rotation