Chat mode, phase 1: grounded streaming chat over your notes

Entry points (no sixth tab): Ask in the Library header (desktop button,
phone icon), Ask about this deck in the deck menu, Ask a question on
study/homework results (compact result travels as context), and a Chat
row in the desktop sidebar. Phones get a full-screen route with back +
New chat; the tab bar steps aside.

- Client-side retrieval: chunk scoped decks (~800 tokens), BM25 against
  the question + recent turns, top chunks under ~7k tokens, each
  labelled with deck + section. Notes come from the deck's stored
  sourceText (already kept for Regenerate); decks without it fall back
  to generated content and the UI says so.
- Stateless server: /api/chat validates against the CHAT_MODELS
  allowlist, trims the history to ~6k tokens, caps context at ~9k and
  streams token/thinking/done/error NDJSON. /api/chat/extract reduces
  attachments to text through the existing vision step.
- UI: user bubbles + full-width assistant text, streaming with stop,
  auto-scroll that pauses with a jump-to-bottom button, safe markdown
  (React nodes, no HTML injection; KaTeX dynamically imported only when
  a message has math), Thinking row for reasoning, copy/regenerate/
  edit-and-resend, model + context pickers (last model remembered),
  composer with visualViewport keyboard handling, safe-area, 16px
  textarea, Enter-to-send on desktop.
- Usage-limit failures keep the draft and show the shared message with
  Settings/Ollama actions; stopping maps the reader abort to a clean
  stopped state; offline disables sending with a reason.
- Settings: Keep notes text for chat toggle; deck menu: Delete notes
  text. RATE_LIMIT_CHAT + CHAT_MODELS in .env.example and README.
- Tests: chat suite (63 checks, stub Ollama) wired into run-all.
  Full set: 12/12 suites, 487 checks. SW -> freezmo-v32.

Also: tests/model-compare.mjs (diagnostic) benchmarks two models on the
same notes (latency, repair rounds, activity types) so the gpt-oss vs
gemma default can be decided on numbers; defaults unchanged.

lib/chat-seed.ts

@@ -0,0 +1,43 @@
+"use client";
+
+/**
+ * Hand-off from a study/homework result into the chat: the compact result
+ * summary and the deck it belongs to travel in sessionStorage and the chat
+ * picks them up on mount, pre-scoped. One-shot, like the deck seed.
+ */
+
+export type ChatSeed = {
+  /** Deck to scope the chat to (when the result belongs to one). */
+  deckId?: string;
+  /** Human label for the context banner ("Study results"). */
+  label: string;
+  /** Compact text sent as an extra context chunk with the first request. */
+  text: string;
+};
+
+const KEY = "freezmo.chat.seed.v1";
+
+export function setChatSeed(seed: ChatSeed): void {
+  try {
+    window.sessionStorage.setItem(KEY, JSON.stringify(seed));
+  } catch {
+    /* private mode */
+  }
+}
+
+export function takeChatSeed(): ChatSeed | null {
+  try {
+    const raw = window.sessionStorage.getItem(KEY);
+    if (!raw) return null;
+    window.sessionStorage.removeItem(KEY);
+    const parsed = JSON.parse(raw) as ChatSeed;
+    if (!parsed || typeof parsed.text !== "string" || !parsed.text.trim()) return null;
+    return {
+      deckId: typeof parsed.deckId === "string" ? parsed.deckId : undefined,
+      label: typeof parsed.label === "string" && parsed.label.trim() ? parsed.label : "Study result",
+      text: parsed.text.slice(0, 6000),
+    };
+  } catch {
+    return null;
+  }
+}