md: toolbar investments

[tvanderstad]

• fixes new styles missing toolbar buttons and keyboard shortcuts #3860
• adds a mobile-only toolbar customization menu
• finally removes our dependency on pulldown_cark (we were using their types in some APIs)

ScreenRecording_01-28-2026.20.MP4

merge blockers:

• ios input broken after accessing the menu
• keyboard shortcuts for new styles

[ad-tra]

looks great!! it brings advanced md features like highlighting and spoilers on mobile, i wouldn't use them otherwise because typing their syntax is annoying.
you'd probably want to hide the camera icon on android as it's not implemented yet