Allow customizing thinking/loading messages via settings.json

It would be great to be able to customize the rotating "thinking" messages shown while Claude is processing (e.g. "Thinking…", "Pondering…") via settings.json, similar to how the status line is configurable.

Example config:

"thinkingMessages": ["Thinking...", "Pondering...", "Nooicing..."]

This would let users personalize the experience without any code changes.