Ctrl+scroll doesn't zoom, and behaves differently in the agent pane

[hamza-usmani]

Steps to reproduce

1. Hold Ctrl and scroll the mouse wheel in a terminal pane.
2. Do the same in an agent pane.

Expected Behavior

Ctrl+scroll zooms text size. This is an accessibility expectation, and the behavior should be identical in both pane types.

Actual Behavior

Ctrl+scroll does not zoom, and the agent pane does not match the terminal pane's behavior either way.

Proposed fix

Relevant code: AppActionHandlers.cpp and the mouse-wheel handling in Pane.cpp. The agent pane runs a TUI in mouse-tracking mode, so wheel events need the same kind of bypass being discussed for selection in the agent-pane input issue.