2337: allow resize terminal

[anhtumai]

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[anhtumai]

Allow resizing the drop-down terminal by dragging its bottom-edge

closes #2337

Reason

We have Ctrl Up and Ctrl Down to resize the height of drop-down terminal, but unless users read the source code they may never discover it. Allowing users to resize by dragging bottom-edge is a discoverable and UX-friendly alternative.

Implementation

Adding a thin drag handler in the bottom of drop-down terminal. When users hold the handler with cursor, it triggers an interactive resizing activity for whole window. When the button is released, the app persists final height percentage to setting, with same mechanism as Ctrl Up/ Ctrl Down

Here is the demo:

Screencast.From.2026-08-21.08-50-01.mp4

[anhtumai]

@Davidy22 I have fixed all your comments in this PR