fix(react-ui): restore sidebar collapse in dev + stop Talk page auto-scroll

[localai-bot]

What

Two React UI regressions surfaced after the console-navigation redesign (#10377):

1. Sidebar won't collapse (dev builds only)

toggleCollapse performed its side effects (localStorage write + sidebar-collapse event dispatch) inside the setCollapsed updater:

setCollapsed(prev => {
  const next = !prev
  localStorage.setItem(...)                   // side effect
  window.dispatchEvent(new CustomEvent(...))  // side effect, fires synchronously
  return next
})

React StrictMode (on in dev, stripped in production) double-invokes state updaters to surface impurity. The synchronous dispatch re-entered setState from the App/Sidebar sidebar-collapse listeners mid-update, so the toggle never committed and the button appeared dead. Production builds don't double-invoke, so only the vite dev server was affected.

Fix: compute next from current state and move the persist + broadcast into the handler body, leaving a pure updater.

2. Talk page anchored to the transcript box on load

Talk.jsx auto-scrolled via transcriptEndRef.current.scrollIntoView(...). The transcript is already its own overflow container (maxHeight: 24rem; overflowY: auto), but scrollIntoView bubbles to every scrollable ancestor including the window, yanking the whole page down to the box on mount. Fix: scroll the transcript container directly so the page stays at the top.

Testing

Verified against a running vite dev server (reproduces both bugs) and a production build (collapse already worked there):

• Collapse: toggle / expand / re-collapse round-trip + persistence across reload all work; .sidebar.collapsed class and .sidebar-is-collapsed layout class apply; width 200px -> 52px.
• Talk: window.scrollY === 0 on load (was scrolling down to the transcript box).
• eslint clean on both files (no new warnings).

Assisted-by: Claude:claude-opus-4-8 [Claude Code]