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.

public/sw.js

@@ -9,7 +9,7 @@
  *
  * Bumping CACHE_VERSION is how a new deploy invalidates old assets.
  */
-const CACHE_VERSION = "freezmo-v34";
+const CACHE_VERSION = "freezmo-v35";
 const SHELL_CACHE = `${CACHE_VERSION}-shell`;
 const ASSET_CACHE = `${CACHE_VERSION}-assets`;