Stop tracking generated Frame Home binaries

Remove generated payload files and the source stamp from the repository while
keeping the installer source.
Update the updater and documentation for the shared Studio and Frame Home releases.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

scripts/frame-payload.sh

@@ -1,34 +0,0 @@
-#!/bin/sh
-# The Steam Frame programs in frame/payload are built on the headset (arm64 SteamOS, its compositor's Vulkan driver)
-# and committed; every Frame Studio download and the Frame Home installer ship them. frame/payload/SOURCE records the
-# source they were built from, so Studio is never released beside an older headset build (Studio would save
-# environments the headset can't open).
-#
-#   scripts/frame-payload.sh stamp    after copying freshly built programs into frame/payload
-#   scripts/frame-payload.sh check    fails when the headset's source changed since (CI runs it before releasing)
-set -eu
-ROOT=$(cd "$(dirname "$0")/.." && pwd)
-STAMP="$ROOT/frame/payload/SOURCE"
-
-# What the headset programs are built from (studio/ is Studio's alone), as the files are now: committed or not.
-source_hash() {
-    list=$(mktemp)
-    (cd "$ROOT" && git -c core.quotepath=off ls-files -- src third_party layer CMakeLists.txt > "$list" &&
-        git hash-object --stdin-paths < "$list" | paste -d ' ' - "$list" | sha256sum | cut -c1-64)
-    rm -f "$list"
-}
-
-case "${1:-}" in
-    stamp) source_hash > "$STAMP"
-           echo "frame/payload/SOURCE: $(cat "$STAMP")" ;;
-    check) want=$(source_hash)
-           have=$(cat "$STAMP" 2>/dev/null || true)
-           if [ "$want" != "$have" ]; then
-               echo "frame/payload is out of date: the headset's source changed since its programs were built." >&2
-               echo "Rebuild frame-home, frame-switcher and fenv-tool on the Frame, copy them into frame/payload/bin," >&2
-               echo "then run scripts/frame-payload.sh stamp (docs/building.md)." >&2
-               exit 1
-           fi
-           echo "frame/payload matches the source ($want)" ;;
-    *) sed -n '2,8p' "$0"; exit 2 ;;
-esac