fix(tools): identify historical camera fallback imagery (#1118)

The CCTV frame proxy marks a Street View fallback with X-CCTV-Source, but the portable source dropped the header and get_cctv_snapshot always reported a current view credited to the camera's agency. The source now keeps the recognised provenance, and the tool labels Street View frames as historical Google imagery, refuses synthetic placeholders, and reports unknown provenance without claiming a current view.

src/layers/cctv/source.js

@@ -3,6 +3,12 @@ import {
   FRAME_ENDPOINT,
   MEDIA_ENDPOINT,
 } from './sourcePolicy.js';
+const FRAME_SOURCE_KINDS = new Set([
+  'upstream-image',
+  'hls-pull',
+  'streetview',
+  'synthetic',
+]);
 function safeNumber(value, fallback = NaN) {
   const n = Number(value);
   return Number.isFinite(n) ? n : fallback;
@@ -51,7 +57,7 @@ export function createCctvSource({
     },
     getFrameUrl: frameUrlFor,
     getMediaUrl: mediaUrlFor,
-    /** Read one current frame through the registered frame endpoint. */
+    /** Read a registered frame and its provenance, including fallback frames. */
     async getFrame(camera, { signal } = {}) {
       signal?.throwIfAborted();
       const response = await fetchImpl(frameUrlFor(camera), {
@@ -62,7 +68,12 @@ export function createCctvSource({
       const bytes = new Uint8Array(await response.arrayBuffer());
       signal?.throwIfAborted();
       const type = response.headers.get('content-type') || '';
-      return { contentType: type.split(';')[0].trim().toLowerCase(), bytes };
+      const sourceKind = response.headers.get('x-cctv-source');
+      return {
+        contentType: type.split(';')[0].trim().toLowerCase(),
+        bytes,
+        sourceKind: FRAME_SOURCE_KINDS.has(sourceKind) ? sourceKind : null,
+      };
     },
   };
 }