feat(display): add display_control CoreGraphics binary, replace displayplacer as primary path

Derived from OSIT MasterKey app (LegacyUtilities.m, Ian Kohl 2019).
Uses CGConfigureDisplayMirrorOfDisplay — native macOS API, no Homebrew dependency.
Handler now tries display_control first; falls back to displayplacer for missing binary
or per-device configStr overrides. Build the binary via scripts/build-display-control.sh
on a Mac (requires Xcode CLT only), then commit resources/bin/display_control.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/build-display-control.sh

@@ -0,0 +1,40 @@
+#!/bin/bash
+# scripts/build-display-control.sh
+# Compile the display_control binary for macOS.
+#
+# Requirements: Xcode Command Line Tools
+#   xcode-select --install
+#
+# Run this on a Mac. Commit the resulting binary to resources/bin/
+# so it is bundled into the packaged Electron app without any Homebrew dependency.
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+SRC="$SCRIPT_DIR/display_control.m"
+OUT_DIR="$REPO_ROOT/resources/bin"
+OUT_BIN="$OUT_DIR/display_control"
+
+if ! command -v clang &>/dev/null; then
+    echo "ERROR: clang not found."
+    echo "Install Xcode Command Line Tools:  xcode-select --install"
+    exit 1
+fi
+
+mkdir -p "$OUT_DIR"
+
+echo "Building display_control..."
+clang -framework Cocoa -framework Carbon \
+    -o "$OUT_BIN" "$SRC"
+
+chmod +x "$OUT_BIN"
+
+echo "Built: $OUT_BIN"
+echo ""
+echo "Test it:"
+echo "  $OUT_BIN status"
+echo "  $OUT_BIN extend"
+echo "  $OUT_BIN mirror"
+echo ""
+echo "Once verified, commit resources/bin/display_control to the repo."