v0.4.0

Added

• Stop a run from the sidebar. While the agent is working, the composer's
  Send button becomes a Stop button (or press Escape); starting a
  new chat also stops an in-flight run. Stopping aborts the streaming request,
  dismisses any open destructive-confirmation modal, and keeps the partial reply
  under a muted "⏹ Stopped" note. This rides the vendored web-component 0.4.0.

Changed

• Vendored bundle → @artooi/ag-ui-web-component 0.4.0 (cancel / Stop
  control, onCancelled, Escape-to-stop, confirmation dismissal).
• Pins django-ag-ui>=0.4,<0.5 (was >=0.3): its guarded stream guarantees
  the Pydantic-AI / model-provider request is torn down when a run is stopped —
  no orphaned generation or runaway token spend — persists the partial
  conversation when a conversation store is configured, and records a run-level
  cancellation audit event.