docs: add TUI screenshot to README and docs homepage

Author: MiniCodeMonkey

README.md

@@ -4,6 +4,8 @@ Build big projects with Claude. Chief breaks your work into tasks and runs Claud
 
 **[Documentation](https://minicodemonkey.github.io/chief/)** · **[Quick Start](https://minicodemonkey.github.io/chief/guide/quick-start)**
 
+![Chief TUI](https://minicodemonkey.github.io/chief/images/tui-screenshot.png)
+
 ## Install
 
 ```bash

docs/index.md

@@ -6,6 +6,9 @@ hero:
   name: Chief
   text: Build Big Projects with Claude
   tagline: Chief breaks your work into tasks. Claude builds them one by one.
+  image:
+    src: /images/tui-screenshot.png
+    alt: Chief TUI
   actions:
     - theme: brand
       text: Get Started