Revise demo execution instructions in README

Updated the README to clarify how to run demos and removed unnecessary lines.

Author: PAXECT-Interface

scripts/demos/README.md

@@ -25,26 +25,21 @@ to verify **bit-identical round-trips** and **cross-OS reproducibility**.
 | 09 | `09_universal_total.py` | Full 3-in-1 universal demo — runs identically on Linux · macOS · Windows · Android · iOS. |
 
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-
 ## ▶️ How to Run (Cross-Platform)
 
 All demos are written in **pure Python 3.12+** and require **no shell scripts**.  
 They run identically on **Linux**, **macOS**, **Windows (WSL / PowerShell)**,  
 **Android (Termux)**, and **iOS (Pyto)**.
 
----
-
 Run any demo / Examples:
 
-
-
-
----
-
-python3 scripts/demos/XX_demo_name.py
+<pre><code>python3 scripts/demos/XX_demo_name.py
+# Examples:
 python3 scripts/demos/00_env_check.py
 python3 scripts/demos/01_quickstart_roundtrip.py
 python3 scripts/demos/09_universal_total.py
+</code></pre>
+