The TUI engine

tui/ is a windowing system on the framebuffer console:

Core

tui_core.c (the event loop + window manager), tui_win.c (windows), tui_menu.c, tui_form.c, tui_panel.c, tui_text.c (widgets), tui_input.c (keyboard routing), tui_hw.c (render diagnostics).

Desktop

tui_desktop.c + tui_dt_*: taskbar, launcher, the apps (files, editor, process/system monitor, network status, sysinfo, clock).

The command bridge

tui_cmd.c enumerates the shell command table through the L1 API (any L1 module may enumerate - l1_ext_shell_list_commands_a_z) and renders it as the launcher: the reference consumer of the extension surface.

Extension surface

tui_ext.h - 37 callable declarations (windows, menus, forms, panels, text). L1 modules build UI through it; the CN variants (tui_cn_*.c) show the pattern with the Chinese layer under them.

Rendering path

Framebuffer geometry comes from the multiboot2 framebuffer tag; the console grid and the 8x16 font engine come up before the IDT does (the boot log order matters - the TUI draws with the same primitives the kernel banner used). tui-test is the in-guest regression suite for all of it.