GPU background rendering (EGL/GLES2) with software chrome, plus expanded tests

The Ken Burns wallpaper pan and dim veil move to the GPU: the lock
surface is wrapped in a wl_egl_window, the wallpaper is a textured quad
whose shader applies the pan transform and veil (GPU bilinear makes
sub-pixel panning free — the ~19ms/frame software bilinear is gone,
idle CPU drops from 40% to ~0%), and the clock/pill/status chrome is
still composed with tiny-skia and composited over. EGL init failure
falls back to the fully-software path unchanged.

Notable fixes along the way:
- Text blending is now destination-aware: the old blend forced output
  alpha to 255, which is correct over the opaque background but made
  every glyph opaque in the chrome-only pixmap the GPU path composites.
- wayland-client switches to its C backend for raw surface pointers,
  and khronos-egl/glow replace a hand-rolled EGL loader.

Tests grew from 72 to 88: GPU pan_region parity with the software path
(and edge/bounds/corner invariants), shader-uniform/EGL-attrib sanity,
chrome bounding-rect tracking, and a pixel-level parity test proving
the GPU split stays within double-rounding ULP range of the single-pass
compose.

Cargo.lock

@@ -122,6 +122,8 @@ dependencies = [
  "bread-utils",
  "breadlock-ui",
  "chrono",
+ "glow",
+ "khronos-egl",
  "pam-client2",
  "serde",
  "serde_json",
@@ -346,6 +348,15 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "dlib"
+version = "0.5.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ab8ecd87370524b461f8557c119c405552c396ed91fc0a8eec68679eab26f94a"
+dependencies = [
+ "libloading",
+]
+
 [[package]]
 name = "downcast-rs"
 version = "1.2.1"
@@ -707,6 +718,18 @@ dependencies = [
  "system-deps",
 ]
 
+[[package]]
+name = "glow"
+version = "0.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c5e5ea60d70410161c8bf5da3fdfeaa1c72ed2c15f8bbb9d19fe3a4fad085f08"
+dependencies = [
+ "js-sys",
+ "slotmap",
+ "wasm-bindgen",
+ "web-sys",
+]
+
 [[package]]
 name = "gobject-sys"
 version = "0.22.6"
@@ -904,6 +927,16 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "khronos-egl"
+version = "6.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6aae1df220ece3c0ada96b8153459b67eebe9ae9212258bb0134ae60416fdf76"
+dependencies = [
+ "libc",
+ "libloading",
+]
+
 [[package]]
 name = "lazy_static"
 version = "1.5.0"
@@ -916,6 +949,16 @@ version = "0.2.189"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3eaf3ede3fee6db1a4c2ee091bf8a8b4dccdc6d17f656fb07896ee72867612f2"
 
+[[package]]
+name = "libloading"
+version = "0.8.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d7c4b02199fee7c5d21a5ae7d8cfa79a6ef5bb2fc834d6e9058e89c825efdc55"
+dependencies = [
+ "cfg-if",
+ "windows-link",
+]
+
 [[package]]
 name = "libm"
 version = "0.2.16"
@@ -1297,6 +1340,12 @@ dependencies = [
  "unicode-script",
 ]
 
+[[package]]
+name = "scoped-tls"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e1cf6437eb19a8f4a6cc0f7dca544973b0b78843adbfeb3683d1a94a0024a294"
+
 [[package]]
 name = "scopeguard"
 version = "1.2.0"
@@ -1969,6 +2018,7 @@ dependencies = [
  "cc",
  "downcast-rs",
  "rustix",
+ "scoped-tls",
  "smallvec",
  "wayland-sys",
 ]
@@ -2075,9 +2125,21 @@ version = "0.31.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d8eab23fefc9e41f8e841df4a9c707e8a8c4ed26e944ef69297184de2785e3be"
 dependencies = [
+ "dlib",
+ "log",
  "pkg-config",
 ]
 
+[[package]]
+name = "web-sys"
+version = "0.3.104"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c435338968042f4f59a557f690a253676d47ce13ceb55d70100e7facf6620a30"
+dependencies = [
+ "js-sys",
+ "wasm-bindgen",
+]
+
 [[package]]
 name = "windows-core"
 version = "0.62.2"