feat(scripts): ship a Gatekeeper bypass README in the DMG

No paid Apple Developer Program membership means no notarization, so
every downloader hits Gatekeeper's "unidentified developer" block on
first launch. Documenting the right-click-Open bypass once in the DMG
itself instead of repeating it in every release's notes.

scripts/package-dmg.sh

@@ -34,6 +34,27 @@ echo "Staging '$APP_NAME.app' ($VERSION build $BUILD)..."
 cp -R "$APP_PATH" "$STAGING_DIR/"
 ln -s /Applications "$STAGING_DIR/Applications"
 
+# Not notarized (no paid Apple Developer Program membership) — Gatekeeper
+# blocks it on a downloader's first launch. This is the standard bypass,
+# shipped in the DMG itself instead of repeated in every release's notes.
+cat > "$STAGING_DIR/Read Me First.txt" <<'EOF'
+Outpost isn't notarized by Apple (that requires a paid Apple Developer
+Program membership), so macOS Gatekeeper will block it on first launch
+with "cannot be opened because the developer cannot be verified."
+
+To open it anyway:
+  1. Drag Outpost.app to Applications.
+  2. Right-click (or Control-click) Outpost.app and choose "Open".
+  3. Click "Open" in the dialog that appears.
+
+You only need to do this once — after that it launches normally.
+
+If macOS instead shows "Outpost is damaged and can't be opened," that's
+the same Gatekeeper quarantine flag, just a different message on newer
+macOS versions. Fix it from Terminal:
+  xattr -cr /Applications/Outpost.app
+EOF
+
 DMG_NAME="${APP_NAME}-${VERSION}.dmg"
 DMG_PATH="$OUT_DIR/$DMG_NAME"
 rm -f "$DMG_PATH"