feat(frontend): restyle ThothII to the Omics Portal (GSD) design system

Adopt the portal's design language so the app embeds seamlessly into its
header/sidebar chrome later:
- Token layer rewritten as raw OKLCH triplets (the previous oklch()-wrapped
  vars produced invalid colors; the UI was effectively unstyled). Values mirror
  GSD: Manrope + Fraunces fonts, #cb333b red brand, warm off-white surfaces,
  pill buttons, brand focus rings. Dark tokens follow .dark or the portal's
  [data-bs-theme=dark].
- Layout: no left sidebar, no header (the portal supplies them). Conversation
  column flush-left with a slim F1-F8 phase strip; session rail moved to the
  RIGHT, mirroring the portal's left sidebar (red section label, red-tint active
  item). Editorial empty state.
- Transcript component now actually renders the streamed assistant turns (the
  store accumulated them but nothing displayed them). Toaster mounted for errors
  (matchMedia polyfill added to the jsdom test setup).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/components/ui/button.tsx

@@ -4,15 +4,15 @@ import { cva, type VariantProps } from "class-variance-authority"
 import { cn } from "@/lib/utils"
 
 const buttonVariants = cva(
-  "group/button inline-flex shrink-0 items-center justify-center rounded-lg border border-transparent bg-clip-padding text-sm font-medium whitespace-nowrap transition-all outline-none select-none focus-visible:border-ring focus-visible:ring-3 focus-visible:ring-ring/50 active:not-aria-[haspopup]:translate-y-px disabled:pointer-events-none disabled:opacity-50 aria-invalid:border-destructive aria-invalid:ring-3 aria-invalid:ring-destructive/20 dark:aria-invalid:border-destructive/50 dark:aria-invalid:ring-destructive/40 [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
+  "group/button inline-flex shrink-0 items-center justify-center rounded-full border border-transparent bg-clip-padding text-sm font-semibold tracking-[0.005em] whitespace-nowrap transition-all outline-none select-none focus-visible:ring-3 focus-visible:ring-ring/25 active:not-aria-[haspopup]:translate-y-px disabled:pointer-events-none disabled:opacity-50 aria-invalid:border-destructive aria-invalid:ring-3 aria-invalid:ring-destructive/20 dark:aria-invalid:border-destructive/50 dark:aria-invalid:ring-destructive/40 [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
   {
     variants: {
       variant: {
-        default: "bg-primary text-primary-foreground hover:bg-primary/80",
+        default: "bg-primary text-primary-foreground hover:bg-[oklch(var(--primary-hover))]",
         outline:
           "border-border bg-background hover:bg-muted hover:text-foreground aria-expanded:bg-muted aria-expanded:text-foreground dark:border-input dark:bg-input/30 dark:hover:bg-input/50",
         secondary:
-          "bg-secondary text-secondary-foreground hover:bg-[color-mix(in_oklch,var(--secondary),var(--foreground)_5%)] aria-expanded:bg-secondary aria-expanded:text-secondary-foreground",
+          "bg-secondary text-secondary-foreground hover:bg-[color-mix(in_oklch,oklch(var(--secondary)),oklch(var(--foreground))_5%)] aria-expanded:bg-secondary aria-expanded:text-secondary-foreground",
         ghost:
           "hover:bg-muted hover:text-foreground aria-expanded:bg-muted aria-expanded:text-foreground dark:hover:bg-muted/50",
         destructive:
@@ -21,15 +21,13 @@ const buttonVariants = cva(
       },
       size: {
         default:
-          "h-8 gap-1.5 px-2.5 has-data-[icon=inline-end]:pr-2 has-data-[icon=inline-start]:pl-2",
-        xs: "h-6 gap-1 rounded-[min(var(--radius-md),10px)] px-2 text-xs in-data-[slot=button-group]:rounded-lg has-data-[icon=inline-end]:pr-1.5 has-data-[icon=inline-start]:pl-1.5 [&_svg:not([class*='size-'])]:size-3",
-        sm: "h-7 gap-1 rounded-[min(var(--radius-md),12px)] px-2.5 text-[0.8rem] in-data-[slot=button-group]:rounded-lg has-data-[icon=inline-end]:pr-1.5 has-data-[icon=inline-start]:pl-1.5 [&_svg:not([class*='size-'])]:size-3.5",
-        lg: "h-9 gap-1.5 px-2.5 has-data-[icon=inline-end]:pr-2 has-data-[icon=inline-start]:pl-2",
+          "h-8 gap-1.5 px-3.5 has-data-[icon=inline-end]:pr-2.5 has-data-[icon=inline-start]:pl-2.5",
+        xs: "h-6 gap-1 px-2.5 text-xs has-data-[icon=inline-end]:pr-1.5 has-data-[icon=inline-start]:pl-1.5 [&_svg:not([class*='size-'])]:size-3",
+        sm: "h-7 gap-1 px-3 text-[0.8rem] has-data-[icon=inline-end]:pr-2 has-data-[icon=inline-start]:pl-2 [&_svg:not([class*='size-'])]:size-3.5",
+        lg: "h-10 gap-1.5 px-5 text-[0.9rem] has-data-[icon=inline-end]:pr-3.5 has-data-[icon=inline-start]:pl-3.5",
         icon: "size-8",
-        "icon-xs":
-          "size-6 rounded-[min(var(--radius-md),10px)] in-data-[slot=button-group]:rounded-lg [&_svg:not([class*='size-'])]:size-3",
-        "icon-sm":
-          "size-7 rounded-[min(var(--radius-md),12px)] in-data-[slot=button-group]:rounded-lg",
+        "icon-xs": "size-6 [&_svg:not([class*='size-'])]:size-3",
+        "icon-sm": "size-7",
         "icon-lg": "size-9",
       },
     },

frontend/src/components/ui/sonner.tsx

@@ -28,9 +28,9 @@ const Toaster = ({ ...props }: ToasterProps) => {
       }}
       style={
         {
-          "--normal-bg": "var(--popover)",
-          "--normal-text": "var(--popover-foreground)",
-          "--normal-border": "var(--border)",
+          "--normal-bg": "oklch(var(--popover))",
+          "--normal-text": "oklch(var(--popover-foreground))",
+          "--normal-border": "oklch(var(--border))",
           "--border-radius": "var(--radius)",
         } as React.CSSProperties
       }