Add raster imagery to the globe contract and draw FIRMS heat and Recent Imagery through it

engine.imagery draws raster layers over the globe: Web Mercator tile
templates and single images or canvases stretched over a rectangle, with
alpha, show, a left/right split against the engine's split position and
an order. A layer's source can be replaced in place.

- Cesium puts one ImageryLayer per layer on the globe's imagery stack,
  or on the shown 3D tileset's when the globe is hidden, and moves it
  when the surface changes; the Recent Imagery request gate moved here.
- Navara draws them in one screen pass after tone mapping that samples up
  to eight layers by geodetic position from mipmapped textures and a tile
  atlas, under the other drapes and engine.ground.
- The fake engine keeps each layer's state.

The FIRMS far-zoom heat raster and Recent Imagery now draw through it, so
FIRMS' heat seam and both its backends, and Recent Imagery's Cesium and
Navara renderers and tile plan, go. Against HEAD, Cesium's pixels are
identical in all four compared scenes; Navara's orbital heat changes by a
mean of 3.8 from new mipmapping, slightly towards Cesium. The contract
suite passes on both engines (Cesium 68/68, Navara 71/71).

engine.maps.addOverlay stays a Navara-only extension for Sea Marks and
Ski Pistes until imagery has a finer tile path for oblique global views.

docs/CURRENT-STATE.md

@@ -183,8 +183,10 @@ one application, and only the globe-bound parts move to the next engine.
   `node scripts/qa-contract-suite.mjs <origin>` runs them in headless Chrome
   on the real Cesium and Navara of a keyless dev server, with a real pointer
   and real canvases; checks of state the app drives itself (contact sonar)
-  are skipped and named. On November 7, 2026 Cesium passed 66 of 66 and
-  Navara 69 of 69. `movers` and `lines` are required of every engine: Cesium
+  are skipped and named. On November 7, 2026, with the imagery checks,
+  Cesium passed 68 of 68 and Navara 71 of 71 (the camera-events check now
+  and then misses its moveEnd on a busy machine on either engine and passes
+  when run again). `movers` and `lines` are required of every engine: Cesium
   draws them with billboards, points, models and polyline primitives
   (`src/globe/cesium/movers.js`, `lines.js`).
 - **Fills on the ground** (`engine.ground`) are required of every engine
@@ -202,6 +204,26 @@ one application, and only the globe-bound parts move to the next engine.
     perimeters have prototypes in `render/ground.js`.
   - On November 7, 2026, `scripts/qa-ground-suite.mjs` (the ground checks
     with pixels) passed 3 of 3 on both engines.
+- **Rasters on the ground** (`engine.imagery`) are required of every engine
+  too: layers of Web Mercator tiles from a URL template or of one image (a
+  canvas, an image, RGBA bytes or an image URL) over a rectangle, each with
+  its alpha, show, split side and draw `order`, and one split position per
+  engine (`docs/GLOBE-PRIMITIVES.md`).
+  - Cesium draws each as an `ImageryLayer` on the imagery stack of the
+    surface shown (the globe, or the shown 3D tileset's), and follows it
+    (`src/globe/cesium/imagery.js`).
+  - Navara draws them in one screen pass after tone mapping, classified on
+    the scene depth (`src/globe/navara/imagery/`).
+  - Active Fires' far-zoom heatmap and Recent Imagery draw through it;
+    weather, wind and the Bhote Koshi event imagery do not yet.
+  - `engine.maps.addOverlay` (Navara's native raster layers for Sea Marks
+    and Ski Pistes) stays until those overlays move to `engine.imagery`.
+  - On November 7, 2026, `scripts/qa-ground-suite.mjs --only=imagery:` (the
+    imagery checks with pixels) passed 2 of 2 on both engines, and
+    `scripts/qa-imagery-compare.mjs` found the heatmap and Recent Imagery
+    drawn as before on Cesium (no pixel changed where they draw) and on
+    Navara (no channel off by more than 1 of 255, but for the heatmap from
+    orbit, which Navara now mipmaps as Cesium does).
 - **Engine coupling.** `node scripts/report-engine-coupling.mjs` counts the
   engine-specific code outside the engines: renderer lines per engine, Cesium
   imports, `viewer` mentions, engine-name checks, raw Navara reads, Navara
@@ -233,11 +255,9 @@ one application, and only the globe-bound parts move to the next engine.
   `src/layers/awareness/render/pulseDisc.js` (`render/cesiumPulses.js`, a
   material disc, on Cesium; `render/navaraPulses.js`, a surface pass that the
   Navara mode loads and passes in).
-  The Active Fires far-zoom heatmap, a raster draped on the ground that the
-  contract has no primitive for yet, draws behind one seam,
-  `src/layers/firms/render/heatField.js` (`render/cesiumHeat.js`, an imagery
-  layer, on Cesium; `render/navaraHeat.js`, a surface pass that the Navara
-  mode loads and passes in). CCTV's monitor plane and viewshed volume, which the
+  The Active Fires far-zoom heatmap is an `engine.imagery` layer, and Recent
+  Imagery draws its days through `engine.imagery` from its own
+  `render/display.js`. CCTV's monitor plane and viewshed volume, which the
   contract has no primitive for yet, draw behind one seam,
   `src/layers/cctv/render/meshes.js` (`render/cesiumMeshes.js` on Cesium;
   `render/navaraMeshes.js`, which the Navara mode loads and passes in). Cesium