Add headless streaming mode + Mac client + full docs

Headless mode (new) — for KVM-attached hosts streaming to disconnected clients
- --headless / --mirror flags; default headless on hostname JARVIS, mirror elsewhere
- New lib/headless.sh installs prep-cmd hooks to ~/.local/share/omarchy-moonlight/bin
- bin/sunshine-stream-do.sh creates/resizes a Hyprland HEADLESS-1 output to the
  connecting client's resolution and migrates the active workspace onto it
- bin/sunshine-stream-undo.sh tears down the headless output on disconnect and
  returns the workspace to a non-headless monitor when one is available
- lib/config.sh writes capture=wlr, output_name=HEADLESS-1, and the JSON
  global_prep_cmd entry referencing the installed hook paths
- lib/preflight.sh adds a preflight_headless step that checks hyprctl, jq, and
  a running Hyprland session (warn-only, install can proceed)
- lib/verify.sh adds checks for the hook scripts and the wlr/global_prep_cmd
  config lines

Mac client
- client/install-macos.sh: Darwin guard, Homebrew presence check, brew cask
  install of Moonlight, idempotent
- client/README.md: per-platform install (macOS / Android / iOS / Apple TV /
  Linux + Steam Deck) and the five-step first-pair walkthrough

Other
- jq added to the helper install set in lib/packages.sh (hooks parse Hyprland
  JSON output)
- README.md rewritten to cover both modes, the new flags, the tuned defaults
  per mode + per vendor, the headless internals, and the client pointer

lib/config.sh

@@ -7,6 +7,7 @@ SUNSHINE_CONF="$SUNSHINE_CONF_DIR/sunshine.conf"
 MANAGED_MARKER="# managed-by: omarchy-moonlight"
 
 write_sunshine_config() {
+  local mode="${1:-mirror}"
   mkdir -p "$SUNSHINE_CONF_DIR"
 
   if [[ -f "$SUNSHINE_CONF" ]] && ! grep -qF "$MANAGED_MARKER" "$SUNSHINE_CONF"; then
@@ -31,19 +32,36 @@ write_sunshine_config() {
       ;;
   esac
 
-  info "Writing tuned $SUNSHINE_CONF (GPU: $GPU_VENDOR)"
+  local capture_block
+  case "$mode" in
+    headless)
+      # wlr capture of the Hyprland headless output that prep-cmd hooks create.
+      # global_prep_cmd is parsed as a JSON array by Sunshine, so keep it on one line.
+      capture_block="# Capture: wlr — captures a Hyprland headless output created on stream start.
+capture = wlr
+output_name = HEADLESS-1
+
+# Hooks that create/resize HEADLESS-1 on stream start and remove it on stop.
+global_prep_cmd = [{\"do\":\"${DO_SCRIPT}\",\"undo\":\"${UNDO_SCRIPT}\"}]"
+      ;;
+    mirror|*)
+      capture_block="# Capture: KMS (DRM) — the right choice on Wayland.
+capture = kms"
+      ;;
+  esac
+
+  info "Writing tuned $SUNSHINE_CONF (GPU: $GPU_VENDOR, mode: $mode)"
   cat >"$SUNSHINE_CONF" <<EOF
 $MANAGED_MARKER
 # Generated by omarchy-moonlight install.sh on $(date -Iseconds)
 # Delete this marker line to take ownership; the installer will then leave the file alone.
 #
-# Tuned for low-latency LAN streaming on Hyprland/Wayland with KMS capture.
+# Tuned for low-latency LAN streaming on Hyprland/Wayland.
 # Tune further via the web UI at https://localhost:47990
 
 sunshine_name = ${HOSTNAME_SHORT}
 
-# Capture: KMS (DRM) — the right choice on Wayland.
-capture = kms
+$capture_block
 
 # Encoder tuned for $GPU_VENDOR
 $encoder_block