fix(replay): unify step indexing, dual-index entity deduplication, and prevent step-4 start bug

- Backend: maintain _step_number_cache in DataEngine and include step_number in all step_updated SSE events (summary, thinking, execution result)
- Admin console: query unassigned trace step_ids in stepless_rows to prevent orphan traces from being lost
- Showcase UI: implement dual-indexed entity deduplication (by step_id and step_number) in extractStepReplayFrames to eliminate phantom ghost steps
- Showcase UI: filter visual screenshot steps before generating sequential 1-based frame numbers, preventing step-4 start and index shift bugs
- Showcase UI: add rawStepNumber and summary properties to StepReplayFrame
- Showcase UI: update FloatingVideoPlayerComponent session reset effect to only reset playback on sessionId change rather than on every stepFrames mutation
- Showcase UI: add stepSeekRequest signal and stepIndex parameter to AgentService.openVideoPlayer
- Unit tests: add Karma and Pytest unit tests verifying step 1 start, dual-indexing, and SSE step_number payloads

apps/admin_console/database/repositories/step_repository.py

@@ -390,20 +390,20 @@ class StepRepository:
 
                 steps.append(step_dict)
 
-            # Fetch step-less tool traces (e.g. planner tools)
+            # Fetch step-less tool traces (e.g. planner tools or turns without recorded step)
             cursor.execute(
                 "SELECT t1.trace_id, t1.parent_trace_id, t1.step_id, t1.type,"
                 " t1.name, t1.timestamp, t1.duration, t1.status, t1.payload,"
                 " t2.name as agent_name FROM traces t1 LEFT JOIN traces t2 ON"
                 " t1.parent_trace_id = t2.trace_id WHERE t1.session_id = ? AND"
-                " (t1.step_id IS NULL OR t1.step_id = '') AND (t1.type = 'tool' OR"
+                " (t1.step_id IS NULL OR t1.step_id = '' OR t1.step_id NOT IN (SELECT step_id FROM steps WHERE session_id = ?)) AND (t1.type = 'tool' OR"
                 " (t1.type = 'llm_call' AND t1.status IN ('failed', 'retrying')) OR (t1.type = 'log'"
                 " AND t1.payload LIKE '%LLM Error:%Pausing execution%' AND NOT EXISTS"
                 " (SELECT 1 FROM traces t3 WHERE t3.session_id = t1.session_id AND"
                 " t3.type = 'llm_call' AND t3.status = 'failed' AND"
                 " ABS(t3.timestamp - t1.timestamp) < 2))) ORDER BY"
                 " t1.timestamp ASC",
-                (session_id,),
+                (session_id, session_id),
             )
             stepless_rows = cursor.fetchall()
             if stepless_rows: