Add an inward glow bleeding from the border over the window

New plugin:hyprchrome:glow_size (px, 0 = off) and glow_strength (0-1)
bleed the border's own gradient inward past the window edge, over the
window's own pixels. Off by default, so existing setups are unchanged.

Drawn into the hole the ring's even-odd fill already leaves behind, from
overlapping layers - one per px of depth - each covering the window edge
inward to a progressively greater depth. Overlapping rather than abutting
disjoint bands avoids an antialiasing seam at every shared edge; the cost
is that a layer composites over every deeper one, so its alpha is solved
outermost-inward from the target profile rather than being it.

That profile is strength * (1 - d/glow)^2.2: steep off the window edge,
easing into a tail that reaches zero tangentially so there's no ring
where it stops.

Corner handling, in order of how much it mattered:
- Each layer's outer edge is the ring's inner boundary verbatim, chamfer
  vertices and all. Anything else detaches the glow from the frame and
  opens a sliver of unpainted window at each corner.
- Each layer's inner edge - which is what the falloff's contours actually
  follow - is filleted in proportion to its own depth, so the glow reads
  as chamfered where it meets the frame and rounder as it fades inward.
- Those inner edges also shrink their chamfer by (2-sqrt2) per px of
  inset. Insetting a chamfered rect while holding the chamfer constant
  moves the 45-degree face in by d*sqrt(2) rather than d, which had the
  glow running ~41% deeper at every corner than along the sides.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/GlobalState.hpp

@@ -33,6 +33,16 @@ struct GlobalState {
           "plugin:hyprchrome:inactive_color",
           "Color (or gradient) of the border on unfocused windows, used when follow_hyprland_border_color is false",
           CHyprColor{RGBAToARGB(0x6C6C6CFF)}),
+        .glowSize = makeShared<IntValue>(
+          "plugin:hyprchrome:glow_size",
+          "How far the border's glow bleeds inward over the window, in pixels (0 disables it)",
+          0,
+          IntValueOptions{.min = 0}),
+        .glowStrength = makeShared<FloatValue>(
+          "plugin:hyprchrome:glow_strength",
+          "Peak opacity of the inward glow at the window edge, 0-1",
+          0.35F,
+          FloatValueOptions{.min = 0.F, .max = 1.F}),
         .titlebarHeight = makeShared<IntValue>(
           "plugin:hyprchrome:titlebar_height",
           "Height of the title bar hanging off the floating top-border cutout, in pixels",
@@ -52,6 +62,8 @@ struct GlobalState {
     HyprlandAPI::addConfigValueV2(plugin, config.followHyprlandBorderColor);
     HyprlandAPI::addConfigValueV2(plugin, config.activeColor);
     HyprlandAPI::addConfigValueV2(plugin, config.inactiveColor);
+    HyprlandAPI::addConfigValueV2(plugin, config.glowSize);
+    HyprlandAPI::addConfigValueV2(plugin, config.glowStrength);
     HyprlandAPI::addConfigValueV2(plugin, config.titlebarHeight);
     HyprlandAPI::addConfigValueV2(plugin, config.titlebarTextSize);
     HyprlandAPI::addConfigValueV2(plugin, config.titlebarFont);