README: add asciinema demo

Author: avelanarius

README.md

@@ -2,7 +2,7 @@
 <img width="50%" alt="gradient engineer" src="https://github.com/user-attachments/assets/b3e10245-205d-40e9-828c-3c8ac1163830" />
 </p>
 
-# Gradient Engineer — 60‑Second Linux Analysis (Nix + LLM)
+# `gradient-engineer` — 60‑Second Linux Analysis (Nix + LLM)
 
 Run the classic [“60‑second Linux Performance Analysis”](https://netflixtechblog.com/linux-performance-analysis-in-60-000-milliseconds-accc10403c55) checklist in one command. A portable Nix toolbox is downloaded on the fly, diagnostics run in parallel with a simple TUI, and an optional AI summary is shown at the end.
 
@@ -14,7 +14,7 @@ Run the classic [“60‑second Linux Performance Analysis”](https://netflixte
 > [!NOTE]  
 > This project is an early experiment.
 
-## Quick start
+## Quick Start
 
 ```bash
 # Any provider works; set one of these env vars to enable AI summary
@@ -30,7 +30,11 @@ Notes:
 - If no key is set, diagnostics still run; only the AI summary is skipped.
 - TUI controls: Tab toggles details; q / Esc / Ctrl+C quits.
 
-## Build from source
+## Demo - See It in Action!
+
+[![asciicast](https://asciinema.org/a/738144.svg)](https://asciinema.org/a/738144)
+
+## Build from Source
 
 ```bash
 cd app