Frame Studio and Frame Home: cross-platform builds

Frame Studio now builds for Windows (x64, x86, ARM64), Linux (x64, x86, ARM64)
and macOS (Apple Silicon, Intel):
- studio/platform.h with Win32 and POSIX implementations (dialogs through
  tinyfiledialogs on Linux/macOS), a GLFW window beside the Win32 one, and a
  platform-neutral frame pacer
- MoltenVK support in the renderer (portability enumeration) and bundled in
  the macOS app
- 32-bit builds: large-address-aware, LZMA packing within a 32-bit address space
- unaligned file reads in the loaders go through loadUnaligned (no UB)
- scripts/build-studio.sh, studio/build_windows.bat [x64|x86|arm64],
  cmake/llvm-mingw.cmake, and a GitHub Actions workflow building every target

Frame Home installs without Studio: frame/install-frame-home.{sh,ps1} and
"Install Frame Home.bat" (packaged as FrameHome-installer.zip).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/debugview/debug.frag

@@ -0,0 +1,15 @@
+#version 450
+// Shaded (spec 0 = 1): faceted from the surface's own slope, so shapes read without any lighting; else flat.
+layout(constant_id = 0) const int kShade = 1;
+layout(location = 0) in vec3 vWorld;
+layout(location = 1) flat in vec4 vColor;
+layout(location = 0) out vec4 outColor;
+void main() {
+    vec3 c = vColor.rgb;
+    if (kShade == 1) {
+        vec3 n = cross(dFdx(vWorld), dFdy(vWorld));
+        float l = dot(n, n) > 1e-20 ? abs(dot(normalize(n), normalize(vec3(0.35, 0.85, 0.4)))) : 1.0;
+        c *= 0.42 + 0.58 * l;
+    }
+    outColor = vec4(c, vColor.a);
+}

tools/debugview/debug.vert

@@ -0,0 +1,13 @@
+#version 450
+// Debug views (HslRenderer::setDebugView): any mesh, drawn by its position alone in a flat colour per draw.
+#extension GL_EXT_multiview : require
+layout(location = 0) in vec3 position;
+struct Draw { mat4 clipFromModel[2]; mat4 worldFromModel; vec4 color; };
+layout(std430, set = 0, binding = 0) readonly buffer Draws { Draw d[]; } draws;   // one per draw (firstInstance)
+layout(location = 0) out vec3 vWorld;
+layout(location = 1) flat out vec4 vColor;
+void main() {
+    gl_Position = draws.d[gl_InstanceIndex].clipFromModel[gl_ViewIndex] * vec4(position, 1.0);
+    vWorld = (draws.d[gl_InstanceIndex].worldFromModel * vec4(position, 1.0)).xyz;
+    vColor = draws.d[gl_InstanceIndex].color;
+}

tools/debugview/gen_debug_spirv.sh

@@ -0,0 +1,22 @@
+#!/bin/sh
+# Regenerates src/debug_spirv.h from debug.vert / debug.frag (needs glslc: the Frame has it in /usr/bin).
+set -e
+cd "$(dirname "$0")"
+glslc -O --target-env=vulkan1.1 -fshader-stage=vert debug.vert -o /tmp/debug.vert.spv
+glslc -O --target-env=vulkan1.1 -fshader-stage=frag debug.frag -o /tmp/debug.frag.spv
+python3 - /tmp/debug.vert.spv /tmp/debug.frag.spv > ../../src/debug_spirv.h <<'PY'
+import struct, sys
+print("#pragma once")
+print("// GENERATED by tools/debugview/gen_debug_spirv.sh from tools/debugview/debug.{vert,frag}. Do not edit by hand.")
+print("//   vert: in vec3 position @0; set0 b0 buffer { Draw { mat4 clipFromModel[2]; mat4 worldFromModel; vec4 color; } d[]; } by gl_InstanceIndex")
+print("//   frag: out = color, faceted shading when spec 0 = 1")
+print("#include <cstddef>\n#include <cstdint>\n")
+for name, path in (("Vert", sys.argv[1]), ("Frag", sys.argv[2])):
+    data = open(path, "rb").read()
+    words = struct.unpack("<%dI" % (len(data) // 4), data)
+    print("static const uint32_t kDebug%sSpirv[] = {" % name)
+    for i in range(0, len(words), 8):
+        print("    " + ",".join("0x%08x" % w for w in words[i:i + 8]) + ",")
+    print("};")
+    print("static const size_t kDebug%sSize = sizeof(kDebug%sSpirv);\n" % (name, name))
+PY