Module layout 

Top-level chrome layout for the TUI main screen.

The main screen has three horizontal bands:

┌────────────────────────────────────┐
│ top bar (1 row, status / device)   │
├────────────────────────────────────┤
│ body (serial pane)                 │
│                                    │
│                                    │
├────────────────────────────────────┤
│ bottom bar (1 row, hint text)      │
└────────────────────────────────────┘

main_chrome splits a Rect into exactly those three bands so the top-level renderer can hand each sub-rect to the right widget.

Functions

main_chrome

Splits the terminal area into top bar (1 row), body (min 1 row), and bottom bar (1 row).