fix re-extract: add heartbeat yield, batch index writes, handle HTTP errors in UI

- Generator now yields a 'status' event immediately so the client can
  distinguish 'working' from 'failed silently before first event'
- Batch mode: call write_activity per file but write index.json and
  athlete.json only once at the end (was O(n²) — 2015 rewrites)
- JS: check r.ok before reading the body stream; show HTTP error detail
  instead of staying stuck at 'Starting…'
- Handle 'status' event type in the progress log

bincio/serve/server.py

@@ -648,13 +648,43 @@ async def admin_reextract_originals(
 
     def event_stream():
         from bincio.extract.strava_api import strava_to_parsed
-        from bincio.extract.ingest import ingest_parsed
+        from bincio.extract.metrics import compute as compute_metrics
+        from bincio.extract.writer import (
+            build_summary, make_activity_id, write_activity,
+            write_index, write_athlete_json,
+        )
         from bincio.render.merge import merge_all
 
+        # Immediate heartbeat so the client knows the connection is alive
+        yield f"data: {json.dumps({'type': 'status', 'message': f'Found {total} originals, starting extraction…'})}\n\n"
+
         imported = 0
         skipped = 0
         errors = 0
-        any_imported = False
+
+        # Load existing index once upfront (to preserve any non-Strava activities)
+        index_path = user_dir / "index.json"
+        if index_path.exists():
+            try:
+                existing_index = json.loads(index_path.read_text(encoding="utf-8"))
+            except Exception:
+                existing_index = {}
+        else:
+            existing_index = {}
+
+        owner = existing_index.get("owner", {"handle": handle})
+        # Seed summaries from whatever already exists in activities/
+        summaries: dict[str, Any] = {s["id"]: s for s in existing_index.get("activities", [])}
+
+        _COMPUTED = {"bas_version", "generated_at", "power_curve", "records", "best_climbs"}
+        athlete_config: dict[str, Any] = {}
+        athlete_path = user_dir / "athlete.json"
+        if athlete_path.exists():
+            try:
+                existing_athlete = json.loads(athlete_path.read_text(encoding="utf-8"))
+                athlete_config = {k: v for k, v in existing_athlete.items() if k not in _COMPUTED}
+            except Exception:
+                pass
 
         for n, orig_path in enumerate(original_files, 1):
             try:
@@ -664,28 +694,36 @@ async def admin_reextract_originals(
                 name = meta.get("name", orig_path.stem)
 
                 parsed = strava_to_parsed(meta, streams)
-
-                from bincio.extract.writer import make_activity_id
                 activity_id = make_activity_id(parsed)
+
                 if (user_dir / "activities" / f"{activity_id}.json").exists():
                     skipped += 1
                     yield f"data: {json.dumps({'type': 'progress', 'n': n, 'total': total, 'name': name, 'status': 'skipped'})}\n\n"
                     continue
 
-                ingest_parsed(parsed, user_dir, privacy="public", rdp_epsilon=0.0001)
+                metrics = compute_metrics(parsed)
+                effective_privacy = parsed.privacy if parsed.privacy is not None else "public"
+                write_activity(parsed, metrics, user_dir, privacy=effective_privacy, rdp_epsilon=0.0001)
+                summary = build_summary(parsed, metrics, activity_id, effective_privacy)
+                summaries[activity_id] = summary
+
                 imported += 1
-                any_imported = True
                 yield f"data: {json.dumps({'type': 'progress', 'n': n, 'total': total, 'name': name, 'status': 'imported'})}\n\n"
             except Exception as exc:
                 errors += 1
                 log.error("reextract[%s]: failed on %s: %s", handle, orig_path.name, exc, exc_info=True)
                 yield f"data: {json.dumps({'type': 'progress', 'n': n, 'total': total, 'name': orig_path.stem, 'status': 'error', 'detail': str(exc)})}\n\n"
 
-        log.info("reextract[%s]: done — imported=%d skipped=%d errors=%d", handle, imported, skipped, errors)
-        if any_imported:
+        # Write index and athlete.json once at the end (not once per activity)
+        if imported > 0:
+            yield f"data: {json.dumps({'type': 'status', 'message': 'Writing index and athlete data…'})}\n\n"
+            write_index(list(summaries.values()), user_dir, owner)
+            write_athlete_json(list(summaries.values()), user_dir, athlete_config)
+            yield f"data: {json.dumps({'type': 'status', 'message': 'Running merge and rebuild…'})}\n\n"
             merge_all(user_dir)
             _trigger_rebuild(handle)
 
+        log.info("reextract[%s]: done — imported=%d skipped=%d errors=%d", handle, imported, skipped, errors)
         yield f"data: {json.dumps({'type': 'done', 'imported': imported, 'skipped': skipped, 'errors': errors})}\n\n"
 
     return StreamingResponse(