feat(intro): v2 — cities, accelerating sweep, detections, thriller sound design

- City engine: Esri ground, OSM buildings that rise with the scan, road
  ribbons carrying modelled traffic coloured by congestion, NYC DOT cameras,
  real ADS-B, MBTA GTFS lines + realtime vehicles, LAX runways with approach
  strobes, Fort Bragg restricted volumes, Everest terrain with contours.
- Indexing keeps accelerating into a 260-capture global sweep while the
  planet whips a full turn.
- The eye opens: aperture blades, sensor array waking, optics calibration,
  radar sweep, orbiting coordinate ring.
- Camera wall with YOLOv8n detections and a city-pulse trace.
- Ends on GOD'S EYE VIEW / OMNISCIENCE.
- audio/sfx.py: sound design only, built to sit under a music track.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01KqP857pippaUs6konSDfe8

intro-sequence/tools/live/fetch_mbta_vehicles.py

@@ -0,0 +1,21 @@
+"""Live MBTA vehicle positions -> city/boston/vehicles.json (square + 1 km)."""
+import json, os, sys, requests
+from collections import Counter
+sys.path.insert(0, os.path.dirname(__file__))
+from common import enu, inside
+ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), '..', '..'))
+j = requests.get('https://cdn.mbta.com/realtime/VehiclePositions_enhanced.json', timeout=30).json()
+rows, total = [], 0
+for e in j['entity']:
+    v = e.get('vehicle') or {}; p = v.get('position') or {}
+    if 'latitude' not in p: continue
+    total += 1
+    x, y = enu('boston', p['latitude'], p['longitude'])
+    if not inside('boston', x, y, 1000): continue
+    rid = (v.get('trip') or {}).get('route_id', '')
+    lab = (v.get('vehicle') or {}).get('label') or (v.get('vehicle') or {}).get('id', '')
+    sp = p.get('speed'); rows.append([x, y, p.get('bearing'), round(sp, 2) if sp is not None else None, rid, lab])
+out = {'t': int(j['header']['timestamp']), 'source': 'cdn.mbta.com VehiclePositions_enhanced.json', 'v': rows}
+json.dump(out, open(os.path.join(ROOT, 'city', 'boston', 'vehicles.json'), 'w'), separators=(',', ':'))
+c = Counter(r[4].split('-')[0] if r[4].startswith(('Green', 'CR')) else ('bus' if r[4][:1].isdigit() or r[4][:2] in ('SL','CT') else r[4]) for r in rows)
+print('t', out['t'], 'feed total', total, 'in square+1km', len(rows), dict(c))