Customize MkDocs theme to match Chainlit UI branding

- Set primary color to match Chainlit submit button (steel blue)
- Add Onest font for text and JetBrains Mono for code
- Use logo-small icon in header (white for dark header) and favicon (dark for browser tab)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: michaelchu

docs/assets/logo-small-dark.png

@@ -0,0 +1,6 @@
+:root {
+  --md-primary-fg-color: hsl(201, 19.3%, 23.3%);
+  --md-primary-fg-color--light: hsl(201, 19.3%, 35%);
+  --md-primary-fg-color--dark: hsl(201, 19.3%, 18%);
+  --md-accent-fg-color: hsl(201, 19.3%, 45%);
+}

docs/assets/logo-small.png

@@ -9,8 +9,13 @@ theme:
   name: material
   palette:
     scheme: default
-    primary: indigo
-    accent: indigo
+    primary: custom
+    accent: custom
+  font:
+    text: Onest
+    code: JetBrains Mono
+  logo: assets/logo-small-dark.png
+  favicon: assets/logo-small.png
   features:
     - navigation.tracking
     - navigation.tabs
@@ -62,6 +67,9 @@ markdown_extensions:
   - attr_list
   - md_in_html
 
+extra_css:
+  - stylesheets/extra.css
+
 plugins:
   - search
   - mkdocstrings: