feat(intro): add the First Light intro sequence

A deterministic WebGL film of God's Eye View coming online: a seed on Null
Island grows into a culture that draws the planet, indexes the surface
tile by tile, ingests the live feeds and outgrows its dish, ending on the
logo. Renders 16:9 and 9:16 frame by frame in headless Chromium; the
procedural score is locked to the same clock. Data and imagery are
fetched by the scripts in tools/ and are not committed.

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

intro-sequence/tools/imagery/build_quadtree_tiles.py

@@ -0,0 +1,15 @@
+"""Deliverable 5: Esri World Imagery z3 (8x8) and z4 (16x16) tiles for the quadtree indexing effect."""
+import os, shutil
+from common import OUT, esri_jobs, fetch_many, esri_tile_path
+
+for z in (3, 4):
+    n = 2 ** z
+    d = os.path.join(OUT, f"tiles_z{z}")
+    os.makedirs(d, exist_ok=True)
+    coords = [(x, y) for y in range(n) for x in range(n)]
+    res = fetch_many(esri_jobs(z, coords), desc=f"esri z{z}")
+    bad = [k for k, v in res.items() if v is None]
+    for x, y in coords:
+        if res[(x, y)] is not None:
+            shutil.copyfile(esri_tile_path(z, x, y), os.path.join(d, f"z{z}_{x}_{y}.jpg"))
+    print(f"z{z}: {len(coords)-len(bad)} tiles written, {len(bad)} failed")