Label the error fences, and settle a tie by where the format writes it

README.md

@@ -356,7 +356,7 @@ always agrees, and the other is a load error. This covers every way a level can
 be rendered: a token, a `{calc()}` operand, and a `{..path}` reference — wherever
 the reference sits, including in a field the format renders.
 
-```
+```text
 token {p} renders a level that {p.first} reads a path into; name the fields you want instead
 ```
 
@@ -381,7 +381,7 @@ nested template keeps its own. A field no dotted token addresses is unaffected:
 `New` checks a path the way `Fake` resolves one: every variant of a multi-variant
 choice must carry the whole path, so a row missing a field is named at load:
 
-```
+```text
 token {place.postal-code}: field "place": not every variant of this 2-way choice
 carries "postal-code"; all carry [locality]
 ```

template.go

@@ -229,7 +229,9 @@ func checkNoOverlap(ops []op, bound map[string]string, format string) error {
 			names = append(names, reader{name, fmt.Sprintf("calc operand %q", name)})
 		}
 	}
-	sort.Slice(names, func(i, j int) bool { return names[i].name < names[j].name })
+	// Stable, so two readers of one name (a token and a calc operand both naming
+	// "p") are reported in the order the format writes them.
+	sort.SliceStable(names, func(i, j int) bool { return names[i].name < names[j].name })
 	for i, level := range names {
 		for _, path := range names[i+1:] {
 			if strings.HasPrefix(path.name, level.name+".") {