Stop telling every desktop that it is KDE

Only GNOME was recognised, and everything else was handed to KWin. On i3,
XFCE, Cinnamon, MATE, sway and the rest, Dikte wrote an entry into
kglobalshortcutsrc that nothing reads, called the session KDE, and
promised that the keys would work after the next login. They never did.

There is no backend to write for any of them. The /dev/input listener is
already desktop-agnostic, so those sessions are the case macOS has always
been: no registry, nothing to install, nothing to remove, and the
combination held by the running process. One backend() function decides
which of the four this session has, and the name shown, the status read
back, what Install writes, what Settings explains and what the installer
promises are all taken from it, so they cannot disagree.

A desktop now only counts when the program that writes its registry is
there too. A GNOME session without gsettings and a Plasma one without
kwriteconfig6 fall to the listener rather than to a file, which is also
how Plasma 5 stops erroring on a kwriteconfig6 it never had.

What Settings shows on those desktops is the truth: no Install button, no
KWin, no listener checkbox (it is the mechanism, not a choice), what
reading /dev/input costs, that the focused application sees the keys too,
and the command to bind if you would rather your desktop owned them. The
evdev listener records what it is listening for the way the Carbon one
does, so the status line has something to say there at all.

Closes #28

README.md

@@ -5,7 +5,8 @@ machine by default, a model cleans it up (dropping the *uh*s, the restarts, the
 missing punctuation), and the result lands in your clipboard and is pasted into
 whatever window you were typing in.
 
-Built for KDE Plasma 6 on Wayland, and runs on GNOME X11 and macOS too. No
+Built for KDE Plasma 6 on Wayland, and runs on GNOME X11, macOS and any other
+Linux desktop that will let it read the keyboard. No
 dependencies beyond system packages: just the Python standard library, 3.11 or
 newer, and PyQt6.
 
@@ -184,14 +185,19 @@ running.
   right-click to delete.
 - **Turkish and English interface**, following the system locale by default.
 
-## The global shortcuts need one logout
+## The global shortcuts, and the logout KDE needs
 
 KWin only reads `kglobalshortcutsrc` at startup, so the shortcuts `install.sh`
 writes will not fire until you log out and back in. Until then, Settings →
 Shortcuts → **built-in listener** reads `/dev/input` and catches the combination
 itself. The difference: it does not swallow the key, so `Ctrl+Space` also reaches
 the focused application (some editors will pop up autocomplete). The listener
-needs your user in the `input` group: `sudo usermod -aG input $USER`.
+needs your user in the `input` group: `sudo usermod -aG input $USER`. On GNOME
+the shortcut works the moment it is installed, and on a desktop that keeps no
+registry at all (i3, XFCE, sway and most others) the listener is the whole
+mechanism: nothing is installed, nothing waits for a logout, and Settings →
+Shortcuts shows the command to bind if you would rather your desktop owned the
+keys.
 
 ## Layout
 
@@ -211,7 +217,7 @@ vad.py            deciding whether a recording holds speech at all
 filetranscribe.py file transcription: ffmpeg, chunking, timestamps
 overlay.py        the corner indicator
 settings_ui.py    settings window
-hotkey.py         KDE shortcut installation, the evdev listener, Carbon on a Mac
+hotkey.py         the desktop's shortcut registry, the evdev listener, Carbon on a Mac
 paste.py          wl-clipboard and ydotool wrappers, pbcopy and CoreGraphics
 trayicon.py       the tray icons, drawn where there is no icon theme
 i18n.py           the string table