docs: correct production hostname; note the scene-filter gotcha and its diagnostics

docs/PAGES.md

@@ -1,7 +1,8 @@
 # Pages
 
-Every HTML page the exhibit serves, and what it's for. Base URL in production:
-`https://newbury.hideawaygaming.com.au/`
+Every HTML page the exhibit serves, and what it's for.
+
+**Production base URL: `https://newburynights.hideawaygaming.com.au/`**
 
 **Keep this current.** When a page is added, renamed, or removed, update this
 file in the same commit — it's the index there is, since there's no `/admin/`
@@ -27,8 +28,8 @@ Open in `EXHIBIT_MODE=dev`; password-protected in `EXHIBIT_MODE=final`
 | `/admin/preview.html` | Virtual Viewport | Live orbit view of whatever ghosts are currently active, straight off the same WebSocket feed as the exhibit. Ground truth when the AR view disagrees. |
 | `/admin/plan.html` | Placement Plan | Measured plan for physically positioning crests and models on the real table. |
 | `/admin/print.html` | Print Crests | Generates printable ArUco markers ("Newbury Crests") at the configured `sizeMM`. |
-| `/admin/calibrate.html` | Calibrate | Camera/marker calibration helper. |
-| `/admin/errors.html` | Client Errors | Errors reported by visitor devices (JS errors, unhandled rejections, ghost build failures). First stop when something works on one phone but not another. |
+| `/admin/calibrate.html` | Calibrate | Camera/marker calibration helper. Detects crests **without** filtering against the scene, so it's the quickest way to prove a printed crest is readable at all. |
+| `/admin/errors.html` | Client Errors | Errors reported by visitor devices (JS errors, unhandled rejections, ghost build and scene-fetch failures). First stop when something works on one phone but not another. |
 | `/admin/login.html` | Login | Only relevant in final mode. |
 
 ## Useful API endpoints
@@ -48,3 +49,16 @@ the rest need auth in final mode.
 | `/api/layouts` | Saved named layouts |
 | `/api/client-errors` | Reported client errors (auth in final mode) |
 | `/ws` | WebSocket: `scene`, `active`, `spawn`, `despawn`, `characters`, `pong` |
+
+## Gotcha worth remembering
+
+Detection filters camera detections against the marker IDs in the **active
+scene**. A crest that isn't an anchor in the current layout is detected and then
+discarded, which used to look exactly like "the camera can't see anything".
+
+- The scene is now fetched over HTTP at start, so a down or flapping WebSocket
+  no longer breaks tracking.
+- The HUD reports `scene N anchors` (or `NOT LOADED`) and `markers 1/2 seen
+  [0,7]` — usable over raw — so a filtered-out crest is visible at a glance.
+- The tracking chip says "Crest N not in this layout" rather than "Point at a
+  Newbury Crest" when this happens.