New ways to resize terminal panes: keybindings and a mouse-draggable grip

What

• New keybindings: ctrl+x with left/up now maps to a pane:grow action, and ctrl+x with right/down maps to a pane:shrink action, added to the list of recognized keybinding actions alongside existing pane navigation actions like pane:pageDown, pane:top, and pane:bottom.
• The plugin panel (the "AbovePrompt" area) gained a mouse-draggable resize grip, sized via a new DOCK_GRIP_COLUMNS constant, for click-and-drag resizing, plus scroll-window logic and an "N more above/below" indicator for panel content that overflows the visible area.

Why Gives users more control over how much screen space panes and the plugin panel take up, either via keyboard shortcuts or by dragging with the mouse.