Street Level: Panoramax review follow-ups (gekh, #1134)

Image loading (photoViewer.js)
- One AbortController per open: a new open, close or unmount stops the
  previous photo's first and sharper downloads (an <img> by src = '').
  A collapsed viewer never falls back to the original; Panoramax's flat
  fallback is the thumbnail. A superseded open resolves quietly.
- Flat HD tracked as "loading" and "shown" apart: a discarded response no
  longer blocks later upgrades, and resizes while it loads ask once.
- No upgrade of the photo still shown while another opens.
- Size limits before decoding: imageSize.js reads JPEG/PNG/WebP/GIF
  headers; more than 64 MP or 16,384 px a side is refused undecoded, an
  <img> that decodes larger is refused and let go, flat HD needs a known
  width of at most 8,192 px, and panoramas always decode with a resize.

Panoramax provider
- Retry-After parsed as seconds or an HTTP date; the browser cannot read
  it here, so busy answers back off 5 s doubling to 300 s, reset once
  answered.
- Headers timed, then the body by an idle timeout (15 s of silence), so a
  slow link still gets its megabyte tiles.
- Cones centre only on the picture shown (onShowing), never on a late
  lookup; lookups nobody waits for are aborted (shared, refcounted).
- onReopen: a GPU reset redraws in the viewer, not through the core.
- Cones draw the home z15 tile at once and add neighbours as they arrive;
  a neighbour that failed is not counted as drawn.
- Coverage tiles decode in ~8 ms slices (a 2 MB z10 tile over Paris was
  one ~85-200 ms task); sorted by measured length without a Map.
- Box search asks for 20, not 100 (the API returns them nearest first).
- looksLikeEmail checks every '@'; creatorOf de-duplicates with a Set.

lineCoverage.js
- A redraw while a swap still builds keeps what is on screen (the swap's
  old lines and its ready new ones) and drops only the unready ones.

Tests for each (mutation-checked), two vacuous tests made real, the
cones' pictures lane and readable()'s busy/timeout paths covered; the
fixture's box search is nearest first. Docs: README filters and share
links, CHANGELOG HD wording, CURRENT-STATE.

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

CHANGELOG.md

@@ -153,13 +153,18 @@
   ← → following the picture's own links. The 360° and since filters apply,
   in the lines and in the lookup. The caption names each picture's author
   and licence (CC BY-SA 4.0, Licence Ouverte 2.0…) and links to it in the
-  Panoramax viewer; HD originals load only for an expanded viewer, once.
-  Share links carry it as `0.m.0_0.r.panoramax-1`. KartaView's photo viewer
+  Panoramax viewer. HD originals load once, only when the viewer is wider
+  than the 2,048 px version (a panorama: expanded), and every download stops
+  when the photo changes; an image whose header declares more than 64 MP is
+  refused before it decodes. Share links carry it as
+  `0.m.0_0.r.google-0*kartaview-0*panoramax-1` (`0.m.0_0.r.panoramax-1` works
+  too). KartaView's photo viewer
   is now shared (`photoViewer.js`, `panorama.js`); in it, for KartaView too,
   Esc clears the selected drive before it collapses the panel. Lines are
   simplified and drawn within a point budget (a tile's unsimplified lines
-  over Paris hung the tab), decoded tiles are kept, and the cones' tiles
-  have their own connection.
+  over Paris hung the tab), decoded in slices so the globe keeps moving,
+  and kept; the cones' tiles have their own connection, and the open
+  picture's tile draws its cones before its neighbours arrive.
 
 - Flights and Military Flights highlight emergency transponder broadcasts in
   fleet billboards, 3D models and Cockpit contacts. Colors update when a status