fix(street-level): modal viewer, pinned redirects, real-route CI checks

From the IC8 review of #768, each with tests that fail before:

- P2: the expanded viewer is a real modal: while it is on screen every
  other <body> child is inert (only the ones it set are restored, on
  shrink, close and destroy, and when Clean View/recording/cockpit hide
  it). The voice pill and toasts are not clickable while it is expanded.
- P2: the tile proxy follows redirects by hand, at most 3 hops, each one
  HTTPS on exactly https://tiles.mapillary.com without credentials;
  anything else is a 502 and the token never leaves that origin.
- P2: the real dev and preview server smoke tests request
  /api/mapillary/status and a tile, and the browser gate first checks the
  server's real status route before any interception, so CI fails if the
  Mapillary plugin is not registered.
- P2: both gates press panel headers through one shared helper
  (scripts/qa-panelDrag.mjs): re-resolve the header until it is under the
  pointer, record what the press hit, wait on the real floating/docked
  state, and retry only a press that provably missed the header.

Verified: unit 5910 pass; fixture gate 17/17; panel gate 5/5; live gate
with a real Mapillary token 22/22.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

CHANGELOG.md

@@ -21,6 +21,8 @@
 
 - Street Level, second review round: the panel no longer reopens itself on every page load (only a user, voice or tool switch-on or an opening photo opens it, and those automatic opens are never stored); a floating panel is pulled back on-screen when its content grows or the window shrinks, and its header can never be dropped under the command dock or the voice pill; the expanded photo hides in Clean View, recording and the cockpit; closing a photo stops sequence playback; a failed sequence load can be retried and leaves no stale image cones. The tile proxy refuses cross-site requests and has a per-IP limit, runs at most six upstream fetches at once, stops a response past its size cap as it streams, counts empty tiles against its caches and answers other upstream refusals with 502. The panel's collapsed state now travels in share links (`ui` token `t`).
 
+- Street Level, third review round: closing a photo, switching the layer off or turning FOLLOW on stops the camera flight toward it (only while that flight is still Street Level's); a slow nearest-photo lookup can no longer replace a newer choice; distances, line densification and mesh sampling go the short way round the date line; image cones and the photo marker no longer show through the globe; a selection change recolours the previous zoom's lines still on screen; mesh sampling keeps to its time budget (a persistent priority queue, work only within range) and moves only the affected cones in place; the expanded viewer is a real modal (the rest of the app is inert while it shows); the tile proxy follows redirects only within the Mapillary tile origin; CI checks the real Mapillary routes.
+
 - Add Norway's road cameras from Statens vegvesen as a CCTV pack. The camera
   list is one keyless GeoJSON request to the agency's OGC API view of its
   DATEX 3.1 CCTV table, so no DATEX account is needed. Every working camera