Add code signing, notarization, and DMG packaging scripts

Enables distributing Galaxy.app to end users without Gatekeeper warnings.
Uses Samsung Developer ID Application certificate with hardened runtime.

Pipeline: cargo bundle → sign.sh → notarize.sh → package.sh → Galaxy.dmg

Entitlements:
- network.client (AWS Bedrock API calls)
- automation.apple-events (osascript for CLI install)
- cs.allow-unsigned-executable-memory (Metal shader compilation)

Orchestration scripts:
- build-debug.sh: full pipeline with debug build
- build-release.sh: full pipeline with release build

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.sh

@@ -0,0 +1,69 @@
+#!/bin/bash
+set -e
+cd "$(dirname "$0")"
+
+SIGNING_IDENTITY="Developer ID Application: SAMSUNG ELECTRONICS AMERICA, INC. (3JU72Z7Y3J)"
+
+if [ "$1" = "--release" ]; then
+    APP_PATH="target/release/bundle/osx/Galaxy.app"
+    DMG_PATH="target/release/bundle/osx/Galaxy.dmg"
+    STAGING_DIR="target/release/bundle/osx/dmg-staging"
+else
+    APP_PATH="target/debug/bundle/osx/Galaxy.app"
+    DMG_PATH="target/debug/bundle/osx/Galaxy.dmg"
+    STAGING_DIR="target/debug/bundle/osx/dmg-staging"
+fi
+
+if [ ! -d "$APP_PATH" ]; then
+    echo "Error: $APP_PATH not found."
+    exit 1
+fi
+
+echo "Verifying app is notarized..."
+xcrun stapler validate "$APP_PATH" || {
+    echo "Error: App does not have a valid notarization ticket. Run ./sign.sh and ./notarize.sh first."
+    exit 1
+}
+
+echo "Preparing DMG staging directory..."
+rm -rf "$STAGING_DIR"
+mkdir -p "$STAGING_DIR"
+cp -R "$APP_PATH" "$STAGING_DIR/"
+ln -s /Applications "$STAGING_DIR/Applications"
+
+echo "Creating DMG..."
+hdiutil detach /Volumes/Galaxy -force 2>/dev/null || true
+rm -f "$DMG_PATH"
+hdiutil create -volname "Galaxy" \
+    -srcfolder "$STAGING_DIR" \
+    -ov -format UDZO \
+    "$DMG_PATH"
+
+echo "Signing DMG..."
+codesign --force --sign "$SIGNING_IDENTITY" --timestamp "$DMG_PATH"
+
+echo "Submitting DMG to Apple notary service..."
+RESULT=$(xcrun notarytool submit "$DMG_PATH" \
+    --keychain-profile notarytool-profile \
+    --wait 2>&1)
+echo "$RESULT"
+
+if ! echo "$RESULT" | grep -q "status: Accepted"; then
+    echo ""
+    echo "Error: DMG notarization was not accepted. Check output above."
+    exit 1
+fi
+
+echo "Stapling notarization ticket to DMG..."
+xcrun stapler staple "$DMG_PATH"
+
+echo "Cleaning up staging directory..."
+rm -rf "$STAGING_DIR"
+
+echo ""
+echo "Verifying final DMG..."
+xcrun stapler validate "$DMG_PATH"
+
+echo ""
+echo "Done. Galaxy.dmg is ready for distribution at:"
+echo "  $DMG_PATH"