Frame Home on a PC with SteamVR (Windows, Linux); thumbnails from the spawn

- src/home_platform.h: what Frame Home and the panel need from the system (paths, finding and stopping each
  other, running a tool, restarting, priorities) for SteamOS, Windows and Linux PCs. On a PC the environments are
  Frame Studio's My Environments; Frame Home's own files in %LOCALAPPDATA%\Frame Home (Windows).
- src/openvr_loader.cpp: a PC build finds SteamVR's own OpenVR library at run time (openvrpaths.vrpath), so it runs
  on any PC with SteamVR; Vulkan through volk. CMake: FRAME_HOME_PC (default on Windows and x86-64 Linux); the Steam
  Frame build is unchanged.
- Windows: Frame Home is SteamVR's home app; SteamVR's classic environment shows a 360-degree picture of the current
  home from its spawn (frame-home --panorama --spawn, made by the panel when the home changes) instead of Aurora
  while Frame Home starts. Linux PCs: the Steam Frame's compositor layer, as on the headset.
- frame/pc: install-frame-home-pc.ps1 (+ .bat): online through SteamVR's API or offline in its config files; the
  SteamVR settings it changes are saved and restored exactly on -Uninstall (tested in a sandbox both ways).
  frame-switcher --uninstall. Studio: Properties > Headset > This PC installs it from pc/ beside Studio.
- Packaging and CI: pc/ in the Windows x64 and Linux x64 Studio downloads; FrameHome-PC-windows-x64.zip.
- Thumbnails come from where Frame Home starts you (the first spawn, eyes 1.6 m up): Studio's saves and the
  panel's (frame-home --snapshot --spawn).
- docs/pc-steamvr.md.

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

scripts/build-studio.sh

@@ -52,7 +52,38 @@ build() {
     "$CMAKE" --build "$dir" --target frame-studio --parallel
 }
 
-# dist/FrameStudio-<target>: the program and, beside it, frame/ (the headset side Studio installs)
+# Frame Home for SteamVR on the computer itself (Windows x64, Linux x64), built from the top-level project into
+# $BUILD/<target>-home. $1 target, then extra cmake arguments.
+build_pc_home() {
+    target=$1; shift
+    dir="$BUILD/$target-home"
+    say "building Frame Home for $target's SteamVR"
+    "$CMAKE" -S "$ROOT" -B "$dir" -DCMAKE_BUILD_TYPE=Release -DFRAME_HOME_PC=ON "$@" > "$dir.configure.log" 2>&1 || {
+        tail -20 "$dir.configure.log"; say "$target: Frame Home configure failed (full log: $dir.configure.log)"; exit 1; }
+    "$CMAKE" --build "$dir" --target frame-home frame-switcher --parallel
+}
+
+# pc/ beside Studio: Frame Home for this computer's SteamVR and its installer (Studio's Headset tab runs it).
+# Windows: SteamVR's home app (install-frame-home-pc.ps1). Linux: the Steam Frame's way, the compositor layer, with
+# the headset's own install.sh.
+stage_pc() {
+    target=$1 stage=$2 home="$BUILD/$1-home"
+    case "$target" in
+        windows-x64) mkdir -p "$stage/pc"
+                     cp "$home/frame-home.exe" "$home/frame-switcher.exe" "$stage/pc/"
+                     cp "$ROOT/frame/pc/install-frame-home-pc.ps1" "$ROOT/frame/pc/Install Frame Home on this PC.bat" \
+                        "$ROOT/frame/pc/Remove Frame Home from this PC.bat" "$stage/pc/" ;;
+        linux-x64)   mkdir -p "$stage/pc/bin" "$stage/pc/layer"
+                     cp "$home/frame-home" "$home/frame-switcher" "$stage/pc/bin/"
+                     ${CXX:-g++} -O2 -shared -fPIC -std=c++17 -fvisibility=hidden -I"$ROOT/third_party/vulkan-headers/include" -I"$ROOT/src" \
+                        "$ROOT/layer/frame_home_layer.cpp" -o "$stage/pc/layer/libframe_home_layer.so" -lpthread
+                     cp "$ROOT/frame/payload/layer/env_ps.spv" "$stage/pc/layer/"
+                     cp "$ROOT/frame/payload/install.sh" "$stage/pc/" && chmod +x "$stage/pc/install.sh" "$stage"/pc/bin/* ;;
+    esac
+}
+
+# dist/FrameStudio-<target>: the program and, beside it, frame/ (the headset side Studio installs) and pc/ (Frame Home
+# for this computer's SteamVR, where there is one)
 package() {
     target=$1 dir="$BUILD/$1" name="FrameStudio-$1"
     stage="$BUILD/stage/$name"
@@ -60,8 +91,10 @@ package() {
     cp "$ROOT/LICENSE" "$stage/LICENSE.txt"
     case "$target" in
         windows-*) cp "$dir/Frame Studio.exe" "$stage/" && cp -R "$dir/frame" "$stage/frame"
+                   stage_pc "$target" "$stage"
                    (cd "$BUILD/stage" && rm -f "$DIST/$name.zip" && zip -qr "$DIST/$name.zip" "$name") ;;
         linux-*)   cp "$dir/Frame Studio" "$stage/" && cp -R "$dir/frame" "$stage/frame"
+                   stage_pc "$target" "$stage"
                    tar -czf "$DIST/$name.tar.gz" -C "$BUILD/stage" "$name" ;;
         macos-*)   cp -R "$dir/Frame Studio.app" "$stage/"
                    bundle_moltenvk "$stage/Frame Studio.app"
@@ -97,10 +130,12 @@ package_frame_home() {
 
 for t in $TARGETS; do
     case "$t" in
-        linux-x64|linux-arm64) build "$t" -G Ninja && package "$t" ;;
+        linux-x64) build "$t" -G Ninja && build_pc_home "$t" -G Ninja && package "$t" ;;
+        linux-arm64) build "$t" -G Ninja && package "$t" ;;
         linux-x86) build "$t" -G Ninja -DCMAKE_C_FLAGS=-m32 -DCMAKE_CXX_FLAGS=-m32 -DCMAKE_SYSTEM_PROCESSOR=i686 \
                        -DCMAKE_LIBRARY_ARCHITECTURE=i386-linux-gnu && package "$t" ;;
-        windows-x64) build "$t" -G Ninja -DCMAKE_TOOLCHAIN_FILE="$ROOT/cmake/llvm-mingw.cmake" -DWINDOWS_ARCH=x86_64 && package "$t" ;;
+        windows-x64) build "$t" -G Ninja -DCMAKE_TOOLCHAIN_FILE="$ROOT/cmake/llvm-mingw.cmake" -DWINDOWS_ARCH=x86_64 &&
+                     build_pc_home "$t" -G Ninja -DCMAKE_TOOLCHAIN_FILE="$ROOT/cmake/llvm-mingw.cmake" -DWINDOWS_ARCH=x86_64 && package "$t" ;;
         windows-x86) build "$t" -G Ninja -DCMAKE_TOOLCHAIN_FILE="$ROOT/cmake/llvm-mingw.cmake" -DWINDOWS_ARCH=i686 && package "$t" ;;
         windows-arm64) build "$t" -G Ninja -DCMAKE_TOOLCHAIN_FILE="$ROOT/cmake/llvm-mingw.cmake" -DWINDOWS_ARCH=aarch64 && package "$t" ;;
         macos-arm64) build "$t" -G Ninja -DCMAKE_OSX_ARCHITECTURES=arm64 -DCMAKE_OSX_DEPLOYMENT_TARGET=11.0 && package "$t" ;;