Fail CI when the manual shows a picture no scene makes

The traceability job now runs `tools/manual/record.sh --check`: every
picture docs/manual/README.md shows must be made by a scene in
tools/manual/scenes.py, and every picture a scene makes must be shown.
It reads the two files and nothing else, so it needs no app, display or
LFS pull.

--changed now dates a scene by the newest commit among its pictures
rather than each picture alone. A scene that also makes a picture which
re-records byte for byte (panorama-aligned beside panorama.gif) no
longer stays listed for ever. A scene all of whose pictures come out
identical (launch) stays listed until one differs, which costs one
harmless re-run.

.gitea/workflows/traceability-check.yml

@@ -67,6 +67,12 @@ jobs:
       # threshold: zero requirements parsed, zero files scanned, a ratio above
       # 100%, or any orphan tag all fail the build. A misconfigured run must not
       # report a plausible-looking 0%.
+      # Every picture the manual shows is made by a scene in
+      # tools/manual/scenes.py, and every picture a scene makes is shown.
+      # Two files read; no app, no display.
+      - name: Manual pictures have scenes
+        run: tools/manual/record.sh --check
+
       - name: Traceability gate
         run: cargo run -q -p traceability -- check
 

tools/manual/scenes.py

@@ -1197,28 +1197,28 @@ def own_code_changed(s, since):
 
 
 def changed():
-    """The scenes whose pictures are older than their sources: for each
+    """The scenes whose pictures are older than their sources: the commit
-    picture, the commit that last touched it, and whether any source — or
+    that last touched any of a scene's pictures, and whether a source — or
     the scene's own code — has changed since (the working tree included).
-    A picture never committed is new, and so is its scene."""
+    A scene none of whose pictures was ever committed is new.
+
+    A re-recording that comes out byte-identical touches no picture, so its
+    scene stays listed until one of its pictures really changes; re-running
+    it is harmless."""
     out = []
     for s in SCENES.values():
-        pics = [m for m in s.media if '.' in m]
+        pics = [f'{MEDIA}/{m}' for m in s.media if '.' in m]
         if not pics:
             continue
-        reasons = []
+        since = git('log', '-1', '--format=%H', '--', *pics).strip()
-        for m in pics:
-            since = git('log', '-1', '--format=%H', '--', f'{MEDIA}/{m}').strip()
         if not since:
-                reasons.append(f'media/{m} was never committed')
+            out.append((s.name, 'its pictures were never committed'))
             continue
         paths = git('diff', '--name-only', since, '--', *[f':(glob){g}' for g in s.sources]).split()
         if paths:
-                reasons.append(f'{", ".join(sorted(set(paths))[:3])} changed since media/{m}')
+            out.append((s.name, f'{", ".join(sorted(set(paths))[:3])} changed since {since[:9]}'))
         elif own_code_changed(s, since):
-                reasons.append(f'its scene changed since media/{m}')
+            out.append((s.name, f'its scene changed since {since[:9]}'))
-        if reasons:
-            out.append((s.name, reasons[0]))
     return out