Align comment parsing with Markdown

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

check.sh

@@ -23,12 +23,14 @@ VISIBLE_BODY=$(printf '%s\n' "${BODY}" | awk '
     if (fence_char == "`" || fence_char == "~") {
       while (substr(line, fence_pos + fence_run, 1) == fence_char) fence_run++
     }
-    if (in_fence) {
+    if (!in_comment && in_fence) {
       print line
       if (fence_char == active_fence_char && fence_run >= active_fence_run) in_fence=0
       next
     }
-    if (fence_run >= 3) {
+    fence_info=substr(line, fence_pos + fence_run)
+    valid_fence_info=(fence_char == "~" || index(fence_info, "`") == 0)
+    if (!in_comment && fence_run >= 3 && valid_fence_info) {
       in_fence=1
       active_fence_char=fence_char
       active_fence_run=fence_run
@@ -52,7 +54,13 @@ VISIBLE_BODY=$(printf '%s\n' "${BODY}" | awk '
         continue
       }
 
-      if (substr(line, pos, 1) == "`") {
+      escaped=0
+      escape_pos=pos - 1
+      while (escape_pos >= 1 && substr(line, escape_pos, 1) == "\\") {
+        escaped++
+        escape_pos--
+      }
+      if (substr(line, pos, 1) == "`" && escaped % 2 == 0) {
         ticks=1
         while (substr(line, pos + ticks, 1) == "`") ticks++
         close_pos=pos + ticks

tests/run

@@ -150,6 +150,15 @@ check_contract "four-space indented backticks do not expose comments" \
 check_contract "unequal backtick runs do not expose comments" \
   $'`<!--``\n## Tracking\n- Fixes bug-x7k2m9 — https://agenthub.fritzlab.net/bug-x7k2m9\n\n## Attribution\n- Authored-By: Codex (GPT-5) <noreply@openai.com>\n-->' \
   "$BASE" "$GOOD_HEAD" "PR body must contain a non-empty ## Tracking section"
+check_contract "invalid backtick fence info does not expose comments" \
+  $'```html`oops\n<!--\n## Tracking\n- Fixes bug-x7k2m9 — https://agenthub.fritzlab.net/bug-x7k2m9\n\n## Attribution\n- Authored-By: Codex (GPT-5) <noreply@openai.com>\n-->' \
+  "$BASE" "$GOOD_HEAD" "PR body must contain a non-empty ## Tracking section"
+check_contract "fences inside comments do not expose provenance" \
+  $'<!--\n```html\n## Tracking\n- Fixes bug-x7k2m9 — https://agenthub.fritzlab.net/bug-x7k2m9\n\n## Attribution\n- Authored-By: Codex (GPT-5) <noreply@openai.com>\n-->' \
+  "$BASE" "$GOOD_HEAD" "PR body must contain a non-empty ## Tracking section"
+check_contract "escaped backticks do not hide a comment opener" \
+  $'\\`<!--\\`\n## Tracking\n- Fixes bug-x7k2m9 — https://agenthub.fritzlab.net/bug-x7k2m9\n\n## Attribution\n- Authored-By: Codex (GPT-5) <noreply@openai.com>\n-->' \
+  "$BASE" "$GOOD_HEAD" "PR body must contain a non-empty ## Tracking section"
 check_contract_pass "inline code containing comment opener stays visible" \
   $'Use `<!--` when documenting an HTML comment opener.\n\n## Tracking\n- Fixes bug-x7k2m9 — https://agenthub.fritzlab.net/bug-x7k2m9\n\n## Attribution\n- Authored-By: Codex (GPT-5) <noreply@openai.com>' \
   "$BASE" "$GOOD_HEAD"