Exclude hidden media fallback provenance

Authored-By: Codex (GPT-5) <noreply@openai.com>

check.sh

@@ -43,7 +43,8 @@ fi
 
 # A collapsed disclosure is valid supporting content, but provenance inside one
 # is not visible by default. Remove only collapsed details subtrees; an open
-# disclosure remains visible unless one of its ancestors is collapsed.
+# disclosure remains visible unless one of its ancestors is collapsed. Media
+# fallback subtrees are likewise hidden when the browser supports the element.
 VISIBLE_BODY=$(printf '%s\n' "${RENDERED_BODY}" |
   awk '
     {
@@ -54,7 +55,11 @@ VISIBLE_BODY=$(printf '%s\n' "${RENDERED_BODY}" |
           tag=tag char
           if (char == ">") {
             lower=tolower(tag)
-            if (lower ~ /^<details([[:space:]>])/) {
+            if (lower ~ /^<(video|audio)([[:space:]>])/) media_depth++
+            else if (lower ~ /^<\/(video|audio)([[:space:]>])/) {
+              if (media_depth > 0) media_depth--
+            }
+            else if (lower ~ /^<details([[:space:]>])/) {
               attributes=lower
               gsub(/"[^"]*"/, "", attributes)
               parent_hidden=(details_depth > 0 && hidden[details_depth])
@@ -67,7 +72,7 @@ VISIBLE_BODY=$(printf '%s\n' "${RENDERED_BODY}" |
                 details_depth--
               }
             }
-            else if (!hidden[details_depth]) printf "%s", tag
+            else if (!hidden[details_depth] && media_depth == 0) printf "%s", tag
             in_tag=0
             tag=""
           }
@@ -76,7 +81,7 @@ VISIBLE_BODY=$(printf '%s\n' "${RENDERED_BODY}" |
           in_tag=1
           tag=char
         }
-        else if (!hidden[details_depth]) printf "%s", char
+        else if (!hidden[details_depth] && media_depth == 0) printf "%s", char
       }
     }
   ')