docs(solo): USB tools and L2 screenshot notes; Units in the L2 settings list

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/solo/developer/build-flags.md

@@ -84,7 +84,7 @@ layered on top of GPS support, not a requirement for it.
 | --- | --- |
 | `OLED_MISC_FIXED_FONT=1` | Pulls in a full Latin/Greek/Cyrillic 6×9 fixed font (~14 KB flash) so typed text in those alphabets renders as itself instead of block placeholders. Worth it on any board with a keyboard; skip it on space-constrained builds without one. |
 | `DISPLAY_ROTATION=<0-3>` | Rotates the panel in 90° steps, for a board mounted sideways or upside down. |
-| `ENABLE_SCREENSHOT` | Lets Solo Tools read the framebuffer over USB to capture a screenshot. |
+| `ENABLE_SCREENSHOT` | Lets the site's [USB tools](https://solo.marekzegarek.com/#pc-tools) (or `tools/screenshot.py`) capture the screen over USB. A colour screen (the L2) renders a fresh frame and sends it as RGB565. |
 | `KEEP_DISPLAY_ON_USB` | Refreshes the auto-off deadline continuously while externally (USB) powered, so the auto-off timer only starts counting once power is actually removed. Off by default because OLED panels burn in quickly with a permanently-lit screen — only worth enabling for an LCD/e-ink target, or a display you don't mind replacing. |
 | `AUTO_OFF_MILLIS=<ms>` | How long the display stays on before auto-off. Default 15000 (15s); `0` disables auto-off entirely. |
 | `UI_RECENT_LIST_SIZE=<n>` | How many entries the recent-activity lists show before scrolling. Default 4. |

docs/solo/hardware.md

@@ -78,7 +78,9 @@ spare the panel.
 ## Wio Tracker L2
 
 - **Buttons**: the top one turns the screen off and on; the side one goes
-  home, and held and let go mutes the sound. Side + top takes a screenshot.
+  home, and held and let go mutes the sound. Side + top takes a screenshot
+  (a BMP in `screenshots/` on the SD card); the site's USB tools take one over
+  USB.
   Holding the side button in the first seconds after power-on starts the CLI
   rescue on USB serial.
 - **SD card**: holds the message history, maps, GPX trails and live map tiles.

docs/solo/navigation.md

@@ -39,8 +39,8 @@ it's connected over USB.
 > **Wio Tracker L2:** the trail holds 4096 points and is drawn on the map.
 > Its controls (start / stop, save, load, track back, reset) are in the map's
 > **Map tools**, the settings in Settings › Map. **GPX** writes the trail to
-> the SD card; take it off with the card as a USB drive
-> ([Hardware](./hardware.md)).
+> `trails/` on the SD card; take it off with the card as a USB drive
+> ([Hardware](./hardware.md)) and open it in the USB tools for a preview.
 
 ## Waypoints
 

docs/solo/settings.md

@@ -37,4 +37,4 @@ A few notes:
 > - **Connections**: Radio, Bluetooth, WiFi, GPS.
 > - **Map & data**: Map (trail, live sharing and arrival alert options),
 >   Storage.
-> - **System**: Name, Time, Firmware update, About; Reboot and Power off.
+> - **System**: Name, Time, Units, Firmware update, About; Reboot and Power off.