Closes https://github.com/zed-industries/zed/issues/39406 Follow up to https://github.com/zed-industries/zed/pull/38726 This PR introduces the `agent_buffer_font_size` setting and renames `agent_font_size` to `agent_ui_font_size`. This allows whoever wants `buffer_font_size` and `agent_buffer_font_size` to match, as well as folks who want a slightly smaller size only in the agent panel (which... also looks just better by default!). Release Notes: - agent: Introduced the `agent_buffer_font_size` setting and renamed `agent_font_size` to `agent_ui_font_size`, allowing for granular buffer font size control in the agent panel vs. regular editors.