Fix two confirmed findings from full codebase audit

- patch_ui.py: wrap shutil.copy2 backup in try/except OSError so a
  permission or read-only filesystem error prints a specific diagnostic
  instead of crashing the script with a generic 'exited non-zero' message
- install.sh: add early guard that detects pipe-install (bash <(curl ...))
  and exits with a clear error pointing to the git clone workflow

patch/patch_ui.py

@@ -90,7 +90,11 @@ def main():
 
     backup = path + ".pre-truecloud-patch"
     if not os.path.exists(backup):
-        shutil.copy2(path, backup)
+        try:
+            shutil.copy2(path, backup)
+        except OSError as exc:
+            print(f"[truecloud-patch] ERROR: Could not create backup {backup}: {exc}")
+            return
 
     patched, count = FIND.subn(REPLACE, content)
     if count != 1: