v1.4.0: smooth flow hand-offs

Added

• Narrated demos: What is Microsoft Access? (English) and ¿Qué es Microsoft Access? (Spanish, three voices), with their scenes in examples/.

Changed

• Flow packets no longer vanish at a component and reappear on the next arrow. When two arrows meet at a component (one multi-arrow flow, or two flows under 2.5 s apart), the packet glides inside, waits while the component's outline fills like a progress ring from where it entered, and glides out onto the next arrow.
• A packet pops out of its source with a small ring, and lands by shrinking into the target with a ripple and a short glow.
• README rewritten: how a request goes, prompts to try, narration languages and voice setup, FAQ.