release: v1.4.2 — Gemini 2.5+ unblocked, auth ContextVar fix, smooth streaming everywhere

- Centralize Gemini 2.5/3 reasoning_effort=none in
  reasoning_params.default_reasoning_effort_for so Visualize / Chat /
  Solve / agentic loop stop returning empty bodies on those models.
- Visualize: per-capability max_tokens default (16k) seeded from
  DEFAULT_AGENTS_SETTINGS, defensive root-tag trim on SVG/HTML output,
  graceful fallback when JSON-mode review step crashes.
- Fix #485: require_auth / require_admin are async so the
  set_current_user ContextVar reaches the endpoint instead of being
  discarded by anyio.to_thread.run_sync's worker-thread context copy.
  Adds _install_current_user helper shared by HTTP + WebSocket.
- Reasoning + native-tools chat protocol: formal content stream must
  still start with FINISH/TOOL/THINK/PAUSE; tool-call deltas no longer
  force-resolve labels and implicit_think_label is ignored, so
  protocol-repair catches missing labels instead of mis-routing turns.
- Smooth streaming on every chat surface: useSmoothStreamText through
  AssistantResponse, pin-to-bottom (useLayoutEffect) on book chat +
  quiz follow-up, data-chat-scroll-root opt-in for overflow-anchor:none.
- Sidebar: collapsible Recents region with own scroll viewport,
  deterministic Lucide icon per session via SessionAvatar, Docs link
  next to GitHub footer, "New Chat" button removed (nav handles it).
- Add Lemonade local provider (port 13305) — registry entry, README
  Docker host-gateway row, providers.md docs.
- Context-window models-endpoint probe honors DISABLE_SSL_VERIFY via
  TCPConnector(ssl=False).
- README: insert v1.4.2 release row, push v1.3.10 inside "Past
  releases" fold, bump install opt-in note to v1.4.2.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>