hermes - 💡(How to fix) Fix feat: add streaming progress callbacks to video_gen so UI can show generation progress

Problem

The generate() method in VideoGenProvider is fully blocking — there is no mechanism for the plugin to emit progress events (e.g., 10% / 50% / 80% complete) that Hermes can relay to connected clients.

Proposed Change

Add an optional on_progress callback to generate():

def generate(self, ..., on_progress: Optional[Callable[[float, str], None]] = None) -> dict:

Motivation

Mother needs to show real-time progress on UI-initiated video generation. Currently running two separate code paths — Hermes plugin for agent-loop (blocking), direct-to-Luma for UI (Trigger.dev with progress events). Streaming callbacks would allow collapsing this asymmetry into a single plugin path.