Move the changelog entry into changelog.d and note seed and datasheet fallbacks

Main takes release notes as one fragment per pull request (#787). A missing value still falls back to a matching seed camera, and a datasheet can still set the field of view.

CHANGELOG.md

@@ -1,19 +1,5 @@
 # Changelog
 
-- Keep missing CCTV numbers unknown instead of reading them as zero. `Number`
-  turns null, blank strings and booleans into 0 or 1, and the camera source
-  list sends an unknown number as JSON null, so a source-pack camera that left
-  out its pose reached the browser as zeros clamped to each field's floor —
-  facing north, pitch −2°, FOV 20°, range 120 m, mount 6 m and ground 0 m —
-  instead of the defaults (id-hash heading, −17°, 74°, 700 m, 24 m and the
-  city's ground); a null or blank position placed the camera at 0,0. The
-  server's `toFiniteNumber` and the browser's `safeNumber` now treat absent,
-  blank and boolean values as missing. The same conversion also stops a
-  Tallinn row with a null heading reading as a confident north-facing camera,
-  a Caltrans camera with a blank elevation losing its 150 m ground prior, and
-  a TfL or Catalonia camera with a null or blank coordinate being kept at 0,0
-  or on the zero meridian.
-
 - Local FM seek finds stations after wrapping around 87.5–108 MHz, covers both
   band edges, skips the starting station and rejects spectra from an earlier
   tune (Aditya, @Rohilalala, #1174).

changelog.d/1172-cctv-missing-numbers.md

@@ -0,0 +1,13 @@
+- Keep missing CCTV numbers unknown instead of reading them as zero. `Number`
+  turns null, blank strings and booleans into 0 or 1, and the camera source
+  list sends an unknown number as JSON null, so a source-pack camera that left
+  out its pose reached the browser as zeros clamped to each field's floor —
+  facing north, pitch −2°, FOV 20°, range 120 m, mount 6 m and ground 0 m —
+  instead of the defaults (id-hash heading, −17°, 74°, 700 m, 24 m and the
+  city's ground); a null or blank position placed the camera at 0,0. The
+  server's `toFiniteNumber` and the browser's `safeNumber` now treat absent,
+  blank and boolean values as missing. The same conversion also stops a
+  Tallinn row with a null heading reading as a confident north-facing camera,
+  a Caltrans camera with a blank elevation losing its 150 m ground prior, and
+  a TfL or Catalonia camera with a null or blank coordinate being kept at 0,0
+  or on the zero meridian (omerbberk, #1172).

docs/CURRENT-STATE.md

@@ -1355,11 +1355,13 @@ browser rendering is unchanged.
 CCTV numbers are read as missing when they are absent, null, blank or boolean,
 on the server (`toFiniteNumber`, every pack and the file/env source packs) and
 in the browser (`safeNumber`). `/api/cctv/sources` sends an unknown number as
-JSON null; the browser then applies the field's default — id-hash heading,
+JSON null; the browser then uses the bundled seed camera's value when one
-pitch −17°, FOV 74°, range 700 m, mount 24 m, the city's ground elevation —
+shares the id, else the field's default — id-hash heading, pitch −17°, FOV 74°
-rather than reading zero and clamping it to the field's floor. A camera with a
+(which a matched datasheet can still replace), range 700 m, mount 24 m, the
-missing latitude or longitude is skipped by the browser catalog instead of
+city's ground elevation — rather than reading zero and clamping it to the
-being placed at 0,0. Real zeros, including `"0"`, are kept.
+field's floor. A camera with a missing latitude or longitude and no seed
+position is skipped by the browser catalog instead of being placed at 0,0.
+Real zeros, including `"0"`, are kept.
 
 ## Terrain, traffic, fire and bike-share provider modules