fix(hyprland): repair master-width, fullscreen, and brightness binds

- `$mod+h`/`l` used dwindle's `splitratio`, a no-op in the master layout;
  switch to `mfact` so they actually resize the master area.
- `$mod+f` ran `fullscreen 1` (maximize, bar/gaps kept); swap so `$mod+f` is
  true fullscreen and `$mod SHIFT+f` maximizes.
- add `$mod+space` `swapwithmaster` (dwm-style zoom).
- the `XF86MonBrightness` binds called `brightnessctl`, which was never
  installed; add the package. It writes via the active logind session.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/home.nix

@@ -136,6 +136,8 @@ in
     libreoffice
     grim        # screenshot capture (also used by the Print-key binds)
     slurp       # interactive region selector for grim
+    brightnessctl  # backlight control for the XF86MonBrightness binds; writes
+                   # via the active logind session, so no udev rule needed
   ];
 
   # Canonical XDG user dirs. Only Pictures is actually used (screenshot target,
@@ -533,8 +535,9 @@ in
         "$mod,		Return,	exec,		foot"
         "$mod,		q,	killactive"
         "$mod SHIFT,	q,	exit"
-        "$mod,		f,	fullscreen,	1"
-        "$mod SHIFT,	f,	fullscreen,	0"
+        # fullscreen arg: 0 = true fullscreen, 1 = maximize (keeps bar/gaps).
+        "$mod,		f,	fullscreen,	0"
+        "$mod SHIFT,	f,	fullscreen,	1"
         "$mod,		w,	exec,		${browser}"
         "$mod,		d,	exec,		fuzzel"
         "$mod,		Backspace,	exec,		${powerMenu}"
@@ -542,8 +545,11 @@ in
         "$mod SHIFT,	j,	layoutmsg,	swapnext"
         "$mod,		k,	layoutmsg,	cycleprev"
         "$mod SHIFT,	k,	layoutmsg,	swapprev"
-        "$mod,		h,	layoutmsg,	splitratio -0.05"
-        "$mod,		l,	layoutmsg,	splitratio +0.05"
+        # swap focused window with the master (dwm-style "zoom").
+        "$mod,		space,	layoutmsg,	swapwithmaster"
+        # master area width. Master layout uses `mfact`, not dwindle's `splitratio`.
+        "$mod,		h,	layoutmsg,	mfact -0.05"
+        "$mod,		l,	layoutmsg,	mfact +0.05"
       ] ++ (
         # Dynamic definitions for viewing workspaces 1 to 9 and moving windows between them.
         # References physical key codes for robustness with the SHIFT key, e.g. `code:10` instead of `1`.