cosmic-conf: translate Hyprland bind lines into COSMIC shortcuts

`bind = SUPER, D, exec, rofi -show drun` is the most recognisable line in a
hyprland.conf, and the hyprcosmic profile makes it necessary rather than just
idiomatic: with cosmic-launcher and cosmic-app-library not running, COSMIC's
stock Super, Super+/ and Super+A bindings point at nothing.

Binds are the one repeatable key in the language -- many lines fold into a
single map instead of the last one winning -- so they bypass the schema, which
is built around one conf key naming one value. They land in the Shortcuts
`custom` key, which cosmic-comp merges over `defaults`, so the system file is
untouched and reverting means deleting the lines and re-applying.

Actions are rendered as RON text rather than modelled as an enum: COSMIC's
Action has forty-odd variants, this crate deliberately does not link the cosmic
crates, and the mapping table only ever needs a handful. Dispatchers without a
genuine equivalent are refused rather than approximated, since a keybinding
that silently does the wrong thing is worse than one that fails to compile.

Verified the emitted file deserializes into cosmic-settings-config's own
`Shortcuts` type: five bindings, keysyms XK_a/XK_slash/XK_Return, Spawn actions.

config/autostart

@@ -13,8 +13,8 @@
 waybar -c /usr/share/hyprcosmic/waybar/config.jsonc -s /usr/share/hyprcosmic/waybar/style.css
 
 # rofi is not a daemon. It is launched on demand by a keybinding, which COSMIC
-# stores in com.system76.CosmicSettings.Shortcuts rather than here. Until that
-# binding is set, run `rofi -show drun` from a terminal.
+# stores in com.system76.CosmicSettings.Shortcuts rather than here. Set those
+# with `bind` lines in cosmic.conf and `cosmic-conf apply`; see config/cosmic.conf.
 
 # HyDE drives wallpaper through swww, which is not packaged for Fedora. Once
 # it is available, uncomment:

config/cosmic.conf

@@ -0,0 +1,28 @@
+# HyprCosmic configuration, in Hyprland's idiom.
+#
+# Compiled into COSMIC's config tree by `cosmic-conf apply`. The file wins:
+# every key here overwrites whatever COSMIC's own settings UI last stored, so
+# edit this rather than the GUI for anything it covers.
+
+$mainMod = SUPER
+
+# --- Launcher -----------------------------------------------------------
+#
+# The hyprcosmic profile does not start cosmic-launcher or cosmic-app-library,
+# which leaves COSMIC's stock Super, Super+/ and Super+A bindings pointing at
+# nothing. These take them over with rofi. Written to the Shortcuts `custom`
+# key, which cosmic-comp merges over `defaults`, so the system file is not
+# touched and reverting is a matter of deleting these lines and re-applying.
+
+# Bare Super, exactly where stock COSMIC puts its launcher.
+bind = $mainMod, , exec, rofi -show drun
+bind = $mainMod, slash, exec, rofi -show drun
+bind = $mainMod, A, exec, rofi -show drun
+
+# Was System(WorkspaceOverview); cosmic-workspaces is not running either.
+# rofi's window mode is the nearest thing that still shows every open window.
+bind = $mainMod, W, exec, rofi -show window
+
+# Terminal, in the Hyprland idiom. Super+T also still works — cosmic-comp
+# handles System(Terminal) itself, so that binding never went dead.
+bind = $mainMod, Return, exec, cosmic-term