fix(ui): include SSE live data when project filter is active (#1315)

When a project filter was selected in the Web UI, all SSE live data
(observations, summaries, prompts) was completely discarded. Only
paginated API data was shown, meaning new real-time events were
invisible until the user refreshed the page.

Fix: filter SSE data by project before merging with paginated data,
instead of discarding it entirely.

Fixes #1313

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

src/ui/viewer/utils/data.ts

@@ -5,10 +5,9 @@
 
 /**
  * Merge real-time SSE items with paginated items, removing duplicates by ID
- * NOTE: This should ONLY be used when no project filter is active.
- * When filtering, use ONLY paginated data (API-filtered).
+ * Callers should pre-filter liveItems by project when a filter is active.
  *
- * @param liveItems - Items from SSE stream (unfiltered)
+ * @param liveItems - Items from SSE stream (pre-filtered if needed)
  * @param paginatedItems - Items from pagination API
  * @returns Merged and deduplicated array
  */