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

bin/sunshine-stream-undo.sh

@@ -0,0 +1,51 @@
+#!/usr/bin/env bash
+# Invoked by Sunshine as a stream-stop hook (global_prep_cmd `undo`).
+# Moves the previously-active workspace back to a real monitor (if any
+# exist) and tears down the headless output created by sunshine-stream-do.sh.
+
+set -euo pipefail
+
+log() { printf '[sunshine-undo] %s\n' "$*" >&2; }
+
+MON="HEADLESS-1"
+STATE_DIR="${XDG_RUNTIME_DIR:-/tmp}/sunshine-headless"
+
+if ! command -v hyprctl >/dev/null 2>&1; then
+  log "hyprctl not found; nothing to undo."
+  exit 0
+fi
+
+if [[ -z "${HYPRLAND_INSTANCE_SIGNATURE:-}" ]]; then
+  for sig_dir in "${XDG_RUNTIME_DIR:-/tmp}"/hypr/*/; do
+    [[ -d "$sig_dir" ]] || continue
+    export HYPRLAND_INSTANCE_SIGNATURE="$(basename "$sig_dir")"
+    break
+  done
+  if [[ -z "${HYPRLAND_INSTANCE_SIGNATURE:-}" ]]; then
+    log "Hyprland not running; nothing to undo."
+    exit 0
+  fi
+fi
+
+PREV_WS="$(cat "$STATE_DIR/prev-workspace-id" 2>/dev/null || echo 1)"
+
+# Find a non-headless monitor to move the workspace back to. If there isn't one
+# (truly headless host with KVM detached), the workspace just lives on whatever
+# Hyprland reassigns it to when we remove the output.
+REAL_MON="$(hyprctl monitors -j 2>/dev/null | jq -r '.[] | select(.name | test("^HEADLESS") | not) | .name' | head -n1)"
+if [[ -n "$REAL_MON" ]]; then
+  log "Returning workspace $PREV_WS → $REAL_MON"
+  hyprctl dispatch moveworkspacetomonitor "$PREV_WS $REAL_MON" >/dev/null || true
+  hyprctl dispatch focusmonitor "$REAL_MON" >/dev/null || true
+else
+  log "No real monitor connected; leaving workspace assignment to Hyprland defaults."
+fi
+
+if hyprctl monitors all -j 2>/dev/null | jq -e --arg m "$MON" '.[] | select(.name == $m)' >/dev/null; then
+  log "Removing $MON"
+  hyprctl output remove "$MON" >/dev/null || true
+fi
+
+# Clean state files but keep the directory for the next run.
+rm -f "$STATE_DIR/prev-monitors.json" "$STATE_DIR/prev-workspace-id"
+log "Stream teardown complete"