website: fix dark mode, table contrast, prose opacity, add AGENTS.md

Dark mode fix: import liveline.css and liveline-prism.css via CSS @import
in globals.css instead of JS import in the route file. This brings them
into the Tailwind compilation chain so @variant dark works. @variant dark
silently fails in CSS files imported only via JS — documented this
constraint in website/AGENTS.md.

- Prism dark colors use CSS variables on :root with @variant dark
- liveline.css dark overrides use @variant dark nested inside selectors
- Table cells use --ll-text-primary for full contrast in both modes
- Prose paragraphs at 0.82 opacity, bold and inline code punch through
  to full opacity for visual hierarchy
- Prose line-height increased to 22px
- Add website/AGENTS.md documenting dark mode rules

website/src/components/markdown.tsx

@@ -214,14 +214,15 @@ export function SectionHeading({ id, children }: { id: string; children: React.R
 export function P({ children, className = "" }: { children: React.ReactNode; className?: string }) {
   return (
     <p
-      className={className}
+      className={`ll-prose ${className}`}
       style={{
         fontFamily: "var(--ll-font-primary)",
         fontSize: "14px",
         fontWeight: 475,
-        lineHeight: "20px",
+        lineHeight: "22px",
         letterSpacing: "-0.09px",
         color: "var(--ll-text-primary)",
+        opacity: 0.82,
         margin: 0,
       }}
     >
@@ -541,7 +542,7 @@ export function ComparisonTable({
                   style={{
                     padding: "4.8px 12px 4.8px 0",
                     fontSize: "11px",
-                    fontWeight: 400,
+                    fontWeight: 500,
                     fontFamily: "var(--ll-font-code)",
                     color: "var(--ll-text-primary)",
                     borderBottom: "1px solid var(--ll-border)",
@@ -554,9 +555,9 @@ export function ComparisonTable({
                   style={{
                     padding: "4.8px 12px 4.8px 0",
                     fontSize: "11px",
-                    fontWeight: 400,
+                    fontWeight: 500,
                     fontFamily: "var(--ll-font-code)",
-                    color: "var(--ll-text-muted)",
+                    color: "var(--ll-text-primary)",
                     borderBottom: "1px solid var(--ll-border)",
                     whiteSpace: "nowrap",
                   }}
@@ -567,9 +568,9 @@ export function ComparisonTable({
                   style={{
                     padding: "4.8px 12px 4.8px 0",
                     fontSize: "11px",
-                    fontWeight: 400,
+                    fontWeight: 500,
                     fontFamily: "var(--ll-font-code)",
-                    color: "var(--ll-text-muted)",
+                    color: "var(--ll-text-primary)",
                     borderBottom: "1px solid var(--ll-border)",
                   }}
                 >