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>

CLAUDE.md

@@ -59,6 +59,8 @@ Config values live under `plugin:hyprchrome:*` and are declared in `src/GlobalSt
 - `extent` (int, px the border extends past the window edge)
 - `follow_hyprland_border_color` (bool) — when true (default), the border tracks Hyprland's own resolved active/inactive border color instead of `active_color`/`inactive_color`
 - `active_color` / `inactive_color` (gradient — one or more colors + optional angle, same syntax as `general:col.active_border`) — used when `follow_hyprland_border_color` is false, or when Hyprland reports no border color at all
+- `glow_size` (int, px the border's color bleeds inward past the window edge, over the window itself — 0, the default, disables it)
+- `glow_strength` (float 0–1, peak opacity of that glow at the window edge, as a fraction of the border color's own alpha)
 - `titlebar_height` (int, px)
 - `titlebar_text_size` (int, px)
 - `titlebar_font` (string, passed to `cairo_select_font_face`)
@@ -79,6 +81,7 @@ Per-window decoration (`src/ChromeDecoration.hpp/.cpp`): implements `IHyprWindow
 - `draw()` doesn't render directly; it enqueues a `ChromePassElement` into Hyprland's render pass each frame.
 - `GetBorderTexture(...)` and `GetTitleTexture(...)` are the actual cairo/Pango rendering entry points, each memoizing against their own last-seen parameters (size, extent, chamfer, color, title text, font, etc.) so unchanged frames reuse the cached `Render::ITexture` instead of re-rendering.
 - `FullDecorationExtentGlobal()` computes the decoration's box in global logical coordinates, accounting for workspace animation offset and floating-window offset.
+- The inward glow (`glow_size`/`glow_strength`) is drawn by `DrawInwardGlow` into the hole the ring's even-odd fill leaves behind, so it lands on the window's own pixels (this decoration is `DECORATION_LAYER_OVER`, and the texture spans the whole window box, not just the ring). Its falloff is built from *overlapping* fills (one layer per px of depth, clamped to `kGlowMinLayers`/`kGlowMaxLayers`) — layer *i* covers the window edge inward to depth `glowPx * i / layers`, so a pixel `d` from the edge is painted by every layer deeper than `d`. The profile is stated explicitly (`strength * (1 - d/glowPx)^kGlowFalloffExponent` — fast off the edge, easing into a tail that reaches zero tangentially so there's no ring where it stops), and since each layer composites over every deeper one, a layer's own alpha is *not* its target: it's solved outermost-inward as `1 - a_j = (1 - T_j) / (1 - T_j+1)`. Changing the profile means changing `targetAt`, not the per-layer alphas. Abutting disjoint bands instead would leave an antialiasing seam at every shared edge; that's the reason for the overlap, don't "optimize" it away. Every layer's *outer* edge is the ring's inner boundary verbatim, chamfer vertices and all — filleting or otherwise altering it detaches the glow from the frame and opens a sliver of unpainted window at each corner. The corner softening lives entirely on the layers' *inner* edges, which are what the accumulated falloff's contours actually follow: each is inset by its own depth, filleted by `kGlowCornerSmoothing` × that depth (`AppendFilletedPolygon`, a quadratic Bezier through each vertex), and has its chamfer shrunk by `kChamferInsetShrink` × that depth. That last correction is not optional cosmetics — insetting a chamfered rect while holding its chamfer constant moves the 45° face in by `d·√2` rather than `d`, so without it the glow runs ~41% deeper at every corner than along the sides. The per-layer alpha is baked into the gradient pattern (`CreateGradientPattern`'s `alphaScale`) specifically so each layer can be a `cairo_fill` of its own band rather than a clip + `cairo_paint_with_alpha`, which would rasterize the clip's full extents — i.e. the whole window area — once per layer.
 
 Render-pass element (`src/ChromePassElement.hpp/.cpp`): an `EK_CUSTOM` pass element (`ChromePassElement::draw()`) that runs once per frame per window and:
 - Derives the corner chamfer live from the window's own `rounding()` (in device px, scaled by monitor scale) — so the border's cut corners track the window's rounding through config reloads, per-window rules, and animations.