Chat layout: history in the main sidebar, consistent header, cleaner icon

- Desktop: on /chat the main sidebar shows the chat list (search, New chat,
  items with rename/delete, active highlight) in place of the deck
  navigation; the separate second column is gone and the chat uses the full
  width. The expand/collapse chevron sits outside the swappable section and
  a collapsed rail stays clean (the highlighted Chat row already opens a
  new chat). Active conversation travels via a tiny store (lib/chat-active)
  so the sidebar needs no useSearchParams and pages stay static.
- Header (phones): history, theme and New chat are now identical chips -
  same 44px hit area, rounded-2xl, border/surface tokens, size-5 icons,
  even spacing; the title block truncates cleanly. ThemeToggle gained a
  'plain' variant so the header styles it without touching other pages.
- ChatIcon redrawn (clean message-circle, no inner lines) and the empty
  state uses the app's icon-chip pattern (size-12 chip, accent-600/200)
  instead of the bare oversized glyph; the model chip icon follows.
- Also fixed a pre-existing dev-only breakage found while verifying: the
  tab-bar bounce animated three keyframes with a spring, which framer
  motion's dev build throws on - breaking client updates in the dev
  instance (library tab switching, sheet Escape). It now uses a tween.
- Dev metadata keeps the Apple icons in both branches.
- SW -> freezmo-v35.

components/TabBar.tsx

@@ -51,7 +51,10 @@ export function TabBar() {
     <motion.span
       key={`${key}-${isActive ? pathname : "idle"}`}
       animate={isActive && !reduceMotion ? { scale: [1, 1.16, 1] } : { scale: 1 }}
-      transition={springSnappy}
+      // A three-keyframe bounce needs a tween: framer-motion's dev build throws
+      // on springs with more than two keyframes (which broke client updates in
+      // the dev instance).
+      transition={isActive && !reduceMotion ? { duration: 0.32, ease: "easeOut" } : springSnappy}
       className="relative z-10 grid place-items-center"
     >
       {children}