v0.6.0

Added

• Thread index for the chat-history drawer (server side).
  ConversationStore gains an async list(*, request) returning owner-scoped
  ConversationMeta (thread_id, title, updated_at, preview) — metadata
  only, no message bodies — so a thread list stays cheap. NullConversationStore
  lists nothing; DjangoSessionConversationStore enumerates the session's own
  threads (titles/previews derived from messages, updated_at stamped on save);
  ModelConversationStore adds a _list(owner_id) hook that defaults to []
  (listing is opt-in, so existing subclasses keep working) and is overridden for
  a cheap column-backed listing.
• ThreadsView, mounted by get_urls(view, threads=<store>) at
  <prefix>threads/ (GET — the user's threads) and <prefix>threads/<id>/
  (GET messages, PATCH rename, DELETE). Every operation is owner-scoped —
  another user's thread reads as 404 — and the view carries the same
  require_authenticated / get_user auth seam as DjangoAGUIView.
• Thread rename. ConversationStore gains rename(thread_id, title, *, request).
  DjangoSessionConversationStore persists the title (it overrides the derived
  one in list); ModelConversationStore adds a _rename(thread_id, title, owner_id) hook that defaults to a no-op (override with a title column);
  NullConversationStore is a no-op. PATCH <prefix>threads/<id>/ takes
  {"title": "..."} — a blank title is 400, a missing/cross-owner thread 404.
• Reference durable store (opt-in). A new django_ag_ui.contrib.store app
  ships a StoredConversation model + migration and DefaultConversationStore
  (a ModelConversationStore subclass implementing fetch/store/remove/list/rename
  with denormalised title/preview/updated_at columns for a cheap thread
  list). Enable it by adding "django_ag_ui.contrib.store" to INSTALLED_APPS,
  running migrate, and pointing DJANGO_AG_UI["CONVERSATION_STORE"] at it.
  The base package still ships no model, so projects that don't opt in get no
  migration.