docs(cctv): document the Toronto pack and the shared camera cap

Adds the Toronto settings to .env.example and a current-state section for the
pack, restores an approximate camera count in the README, and corrects the
claim that adding a pack never trims another region: with the shared
4,000-camera cap, the largest packs give way round-robin. Fixes two stale
comments about the list's refresh and the ground-height sidecar.

.env.example

@@ -226,6 +226,9 @@ AISSTREAM_API_KEY=
 # CCTV_NYC_ENABLED=                                    # off by default; set 1 only if you hold a NYC DOT data-sharing agreement ([email protected]) for the camera feed
 # CCTV_NYC_MAX_SOURCES=250                             # cap cameras loaded from the NYC TMC catalog (nearest borough cores first)
 # CCTV_NYC_CAMERAS_URL=                                # override the NYC TMC catalog URL
+# CCTV_TORONTO_ENABLED=1                              # set 0 to disable the City of Toronto RESCU cameras
+# CCTV_TORONTO_MAX_SOURCES=336                         # cap cameras loaded from Toronto RESCU (clamped to 8–500)
+# CCTV_TORONTO_LIST_URL=                               # override the Toronto RESCU camera list URL
 # CCTV_MAX_SOURCES=4000                                # catalog-wide ceiling, shared round-robin across packs
 # CCTV_PREFER_AUSTIN=1                                 # prioritize Austin cameras in the registry
 # CCTV_FORCE_AUSTIN=                                   # force live default sources when a source-pack JSON is configured