fix(vegas): keep plugin data and visuals fresh during Vegas scroll mode (#291)

* fix(vegas): keep plugin data and visuals fresh during Vegas scroll mode

Plugins using ESPN APIs and other data sources were not updating during
Vegas mode because the render loop blocked for 60-600s per iteration,
starving the scheduled update tick. This adds a non-blocking background
thread that runs plugin updates every ~1s during Vegas mode, bridges
update notifications to the stream manager, and clears stale scroll
caches so all three content paths (native, scroll_helper, fallback)
reflect fresh data.

- Add background update tick thread in Vegas coordinator (non-blocking)
- Add _tick_plugin_updates_for_vegas() bridge in display controller
- Fix fallback capture to call update() instead of only update_data()
- Clear scroll_helper.cached_image on update for scroll-based plugins
- Drain background thread on Vegas stop/exit to prevent races

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(vegas): address review findings in update pipeline

- Extract _drive_background_updates() helper and call it from both the
  render loop and the static-pause wait loop so plugin data stays fresh
  during static pauses (was skipped by the early `continue`)
- Remove synchronous plugin.update() from the fallback capture path;
  the background update tick already handles API refreshes so the
  content-fetch thread should only call lightweight update_data()
- Use scroll_helper.clear_cache() instead of just clearing cached_image
  so cached_array, total_scroll_width and scroll_position are also reset

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Chuck <chuck@example.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/vegas_mode/plugin_adapter.py

@@ -408,7 +408,10 @@ class PluginAdapter:
             original_image = self.display_manager.image.copy()
             logger.info("[%s] Fallback: saved original display state", plugin_id)
 
-            # Ensure plugin has fresh data before capturing
+            # Lightweight in-memory data refresh before capturing.
+            # Full update() is intentionally skipped here — the background
+            # update tick in the Vegas coordinator handles periodic API
+            # refreshes so we don't block the content-fetch thread.
             has_update_data = hasattr(plugin, 'update_data')
             logger.info("[%s] Fallback: has update_data=%s", plugin_id, has_update_data)
             if has_update_data:
@@ -582,6 +585,28 @@ class PluginAdapter:
             else:
                 self._content_cache.clear()
 
+    def invalidate_plugin_scroll_cache(self, plugin: 'BasePlugin', plugin_id: str) -> None:
+        """
+        Clear a plugin's scroll_helper cache so Vegas re-fetches fresh visuals.
+
+        Uses scroll_helper.clear_cache() to reset all cached state (cached_image,
+        cached_array, total_scroll_width, scroll_position, etc.) — not just the
+        image.  Without this, plugins that use scroll_helper (stocks, news,
+        odds-ticker, etc.) would keep serving stale scroll images even after
+        their data refreshes.
+
+        Args:
+            plugin: Plugin instance
+            plugin_id: Plugin identifier
+        """
+        scroll_helper = getattr(plugin, 'scroll_helper', None)
+        if scroll_helper is None:
+            return
+
+        if getattr(scroll_helper, 'cached_image', None) is not None:
+            scroll_helper.clear_cache()
+            logger.debug("[%s] Cleared scroll_helper cache", plugin_id)
+
     def get_content_type(self, plugin: 'BasePlugin', plugin_id: str) -> str:
         """
         Get the type of content a plugin provides.