liveline: add Link component, OL, remove BackButton, dedent code blocks, spacing tweaks

- Add A (link) component with --ll-accent color, bright #58a6ff in dark mode
- Add OL (ordered list) component for numbered steps
- Remove BackButton from EditorialPage
- Use string-dedent for all CodeBlock strings, properly indented in source
- Getting started steps as OL with clickable Chrome Web Store link
- Star on GitHub link in intro paragraph
- Inline heading rule (flex + 1px line) replaces separate Divider
- Heading padding 24px top/bottom, article gap 32px
- Sidebar TOC item spacing increased to 5px
- Centered image captions

website/src/styles/liveline.css

@@ -79,6 +79,9 @@
     rgba(0, 0, 0, 0.04) 0px 4px 16px,
     rgba(0, 0, 0, 0.06) 0px 0px 0px 1px inset;
 
+  /* Link accent color */
+  --ll-accent: #0969da;
+
   /* P3 accent colors (wider gamut) */
   --ll-primary: #3e9fff;
   --ll-secondary: #f09637;
@@ -130,6 +133,7 @@
     rgba(255, 255, 255, 0.02) 0px 4px 16px,
     rgba(255, 255, 255, 0.06) 0px 0px 0px 1px inset;
 
+  --ll-accent: #58a6ff;
   --ll-primary: #60a5fa;
   --ll-secondary: #f5a623;