Add a solid outline tracing the frame's outer edge

New plugin:hyprchrome:outline_size (px, 0 = off) and outline_color
(default white) stroke the frame's outer silhouette - chamfers, title bar
plateau and side notches - with a flat color, so it reads as a drawn line
against the gradient-filled frame underneath. Off by default.

The line sits inside the frame rather than centred on the silhouette. The
outer path runs along the texture's own bounds, so half of a centred
stroke would fall off the surface and vanish on exactly those sides;
stroking at double width leaves the inner half, which comes to
outline_size on every edge.

The clip is the whole ring rather than just the outer path, so an outline
thicker than the frame stops at the window's edge instead of spilling
across the ring onto the window, and a miter spike at the plateau's dip
stays confined to the frame.

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

CLAUDE.md

@@ -61,6 +61,8 @@ Config values live under `plugin:hyprchrome:*` and are declared in `src/GlobalSt
 - `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)
+- `outline_size` (int, px thickness of the solid line tracing the frame's edges — 0, the default, disables it)
+- `outline_color` (color, default white)
 - `shadow_size` (int, px the frame's drop shadow reaches past its own outline — 0, the default, disables it)
 - `shadow_color` (color, its alpha being the shadow's opacity)
 - `shadow_offset` (vec2, px the shadow is displaced by; positive is right/down)
@@ -85,6 +87,7 @@ Per-window decoration (`src/ChromeDecoration.hpp/.cpp`): implements `IHyprWindow
 - `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. It deliberately excludes the drop shadow (below), which is drawn outside it.
 - `GetShadowTexture(...)` renders the drop shadow. The silhouette is `AppendFrameOuterPath` — the same outline `GetBorderTexture` fills, extracted specifically so the two can't drift apart — filled solid into an A8 mask, blurred, then tinted. Three things about it are load-bearing: (1) the window's interior is cleared *after* the blur, not before, since punching it first would smear shadow inward across the window's own content; the cut lands exactly on the ring's inner boundary so the frame's opaque pixels hide it. (2) The shadow is not part of `getPositioningInfo`'s reserved extents — reserving it would push neighbouring windows away by the shadow's width — so it's simply drawn past the decoration's box, which is why `damageEntire()` and `boundingBox()` have to expand by `ShadowMarginLogical()` by hand. (3) It's rendered at most `kShadowMaxDim` px on the long edge and upscaled by the GPU; a blurred blob loses nothing to that, and it caps a cost that would otherwise be paid per frame of a resize animation. The blur itself is three box passes (`BlurA8Surface`), transposing between each so the vertical pass reuses the horizontal one's cache-friendly row code.
+- The solid outline (`outline_size`/`outline_color`) is drawn by `DrawOutline`, tracing the frame's outer silhouette only. It sits *inside* the frame rather than centred on that edge: the outer path runs along the texture's own bounds, so half of a centred stroke would fall off the surface and vanish on those sides. Stroking at double width leaves exactly the inner half, which comes out to `outline_size` on every edge. The clip is the whole ring rather than just the outer path, so an outline thicker than the frame stops at the window's edge instead of spilling onto the window, and a miter spike at the plateau's dip stays confined to the frame.
 - 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: