Chat mode, phase 2: local history, answer actions, motion polish

- Conversations in a versioned IndexedDB store (freezmo-chat v1, zod
  validated with the same schema backup/sync use, capped at 100 x 300).
  Settled turns persist (question always; answer when produced, partial
  stops included); ?c=<id> keeps reloads on the conversation via
  history.replaceState (no router round-trip mid-chat).
- History UI: desktop column, phone sheet (spring, backdrop, Escape),
  auto titles from the first question, inline rename, delete with an
  Undo toast, diacritic-folding search over titles and message text.
  Scope and model are remembered per conversation; history is readable
  offline.
- Assistant actions: Turn into flashcards (New deck with the answer as
  notes, landing on the options step - deck seed gained step) and Save
  to notes (appends to the single scoped deck, trimmed at 40k).
- Chats travel in the backup export (preview counts them) and in the
  encrypted sync payload; still never the key.
- Motion from lib/motion.ts: message fade-up, sheet springs for the
  model/context/history sheets, 150ms composer height transition, all
  skipped under reduced motion.
- Tests: chat suite 63 -> 89 checks (history, reload, rename/search/
  delete/undo, actions, export, two-device sync round-trip, offline,
  desktop panel). Full set: 12/12 suites, 513 checks. SW -> freezmo-v33.

Also: tests/model-compare.mjs benchmark (diagnostic) for deciding the
default text model on numbers; defaults unchanged.

components/chat/ContextPicker.tsx

@@ -1,9 +1,11 @@
 "use client";
 
 import { useEffect } from "react";
+import { AnimatePresence, motion, useReducedMotion } from "framer-motion";
 
 import { CheckCircleIcon, FolderIcon, LayersIcon } from "@/components/icons";
 import { useI18n } from "@/lib/i18n";
+import { springSheet } from "@/lib/motion";
 import { useIsPhone } from "@/lib/use-phone";
 import { deckHasNotes } from "@/lib/chat-context";
 import type { ChatScope } from "@/lib/chat";
@@ -31,6 +33,7 @@ export function ContextPicker({
 }) {
   const { t, plural } = useI18n();
   const isPhone = useIsPhone();
+  const reduceMotion = useReducedMotion();
 
   useEffect(() => {
     if (!open) return;
@@ -41,8 +44,6 @@ export function ContextPicker({
     return () => window.removeEventListener("keydown", onKey);
   }, [open, onClose]);
 
-  if (!open) return null;
-
   const selected = scope.kind === "decks" ? new Set(scope.deckIds) : new Set<string>();
 
   const choose = (next: ChatScope) => {
@@ -171,29 +172,56 @@ export function ContextPicker({
 
   if (isPhone) {
     return (
-      <div className="fixed inset-0 z-50" role="dialog" aria-modal="true" aria-label={t("chat.scope.title")}>
-        <button type="button" className="absolute inset-0 bg-black/45" aria-label={t("common.close")} onClick={onClose} />
-        <div className="glass-panel absolute inset-x-0 bottom-0 max-h-[85dvh] overflow-y-auto rounded-b-none px-4 pb-safe pt-2">
-          <div className="sheet-grabber mx-auto" aria-hidden />
-          <h2 className="px-1 pb-3 pt-2 text-[15px] font-semibold text-[var(--text)]">{t("chat.scope.title")}</h2>
-          {body}
-          <p className="px-1 py-3 text-[11.5px] text-[var(--text-subtle)]">{t("chat.scope.note")}</p>
-        </div>
-      </div>
+      <AnimatePresence>
+        {open ? (
+          <div className="fixed inset-0 z-50" role="dialog" aria-modal="true" aria-label={t("chat.scope.title")}>
+            <motion.button
+              type="button"
+              initial={{ opacity: 0 }}
+              animate={{ opacity: 1 }}
+              exit={{ opacity: 0 }}
+              transition={reduceMotion ? { duration: 0 } : undefined}
+              className="absolute inset-0 bg-black/45"
+              aria-label={t("common.close")}
+              onClick={onClose}
+            />
+            <motion.div
+              initial={reduceMotion ? { opacity: 0 } : { y: "100%" }}
+              animate={reduceMotion ? { opacity: 1 } : { y: 0 }}
+              exit={reduceMotion ? { opacity: 0 } : { y: "100%" }}
+              transition={reduceMotion ? { duration: 0 } : springSheet}
+              className="glass-panel absolute inset-x-0 bottom-0 max-h-[85dvh] overflow-y-auto rounded-b-none px-4 pb-safe pt-2"
+            >
+              <div className="sheet-grabber mx-auto" aria-hidden />
+              <h2 className="px-1 pb-3 pt-2 text-[15px] font-semibold text-[var(--text)]">{t("chat.scope.title")}</h2>
+              {body}
+              <p className="px-1 py-3 text-[11.5px] text-[var(--text-subtle)]">{t("chat.scope.note")}</p>
+            </motion.div>
+          </div>
+        ) : null}
+      </AnimatePresence>
     );
   }
 
   return (
-    <div
-      className="glass-panel absolute bottom-full left-0 z-40 mb-2 w-96 p-3"
-      role="dialog"
-      aria-label={t("chat.scope.title")}
-    >
-      <h2 className="px-1 pb-2 text-[13px] font-semibold uppercase tracking-wide text-[var(--text-subtle)]">
-        {t("chat.scope.title")}
-      </h2>
-      {body}
-      <p className="px-1 pt-2 text-[11.5px] text-[var(--text-subtle)]">{t("chat.scope.note")}</p>
-    </div>
+    <AnimatePresence>
+      {open ? (
+        <motion.div
+          initial={reduceMotion ? { opacity: 0 } : { opacity: 0, y: 6, scale: 0.98 }}
+          animate={{ opacity: 1, y: 0, scale: 1 }}
+          exit={reduceMotion ? { opacity: 0 } : { opacity: 0, y: 6, scale: 0.98 }}
+          transition={reduceMotion ? { duration: 0 } : { duration: 0.16, ease: "easeOut" }}
+          className="glass-panel absolute bottom-full left-0 z-40 mb-2 w-96 p-3"
+          role="dialog"
+          aria-label={t("chat.scope.title")}
+        >
+          <h2 className="px-1 pb-2 text-[13px] font-semibold uppercase tracking-wide text-[var(--text-subtle)]">
+            {t("chat.scope.title")}
+          </h2>
+          {body}
+          <p className="px-1 pt-2 text-[11.5px] text-[var(--text-subtle)]">{t("chat.scope.note")}</p>
+        </motion.div>
+      ) : null}
+    </AnimatePresence>
   );
 }