feat(ui): HDMI refresh boost in the app

Set up… opens a screen with the display, its resolution and the rates on
offer. The display's own faster mode is switched to right away; the other
rates can each be tried live (wait for the picture, keep within 15 s or it
switches back) and ticked; Install installs the ticked ones through
apply --hdmi. All rates are loaded when the screen opens, so a try is only a
mode switch. Also fixes switching back to a rate like 59.97 Hz.

CHANGELOG.md

@@ -11,10 +11,19 @@ one per merged pull request.
   - A graphical app for controller, keyboard and TV remote, driving the same
     components through `steamify.sh --backend`; the BIOS update with both
     warnings; built by GitHub and run with curl.
-- **feat(ui): HDMI refresh boost in the app, off only**
-  - Each step needs someone at the keyboard, so it's turned on from the
-    menu in Konsole; the app can only turn it off. Unticking Steam Machine
-    support or the kernel pin unticks it, as in the menu.
+- **feat(ui): HDMI refresh boost in the app**
+  - "Set up…" opens its own screen: the display, its resolution and the
+    rates on offer (its own mode, calculated tens, the HDMI 2.0 limit). The
+    display's own faster mode is switched to right away; every other rate
+    has a Try button (switch live, wait for the picture, then keep it within
+    15 s or it switches back) and a tick box. Install installs the ticked
+    rates. All rates are loaded when the screen opens, so a try is only a
+    mode switch.
+  - Unticking Steam Machine support or the kernel pin unticks it, as in the
+    menu.
+- **fix(ui): The details panel scrolls instead of overflowing**
+- **fix: Switching back to a rate like 59.97 Hz**
+  - `hdmi_set_mode` compared it as a whole number and printed an error.
 
 ## 1.2.0 - 2026-09-25