Tests for a name no token can spell

A dot is already rejected in a category, folder or field name. The token
grammar reserves three more characters: '|' separates a token's arms, '('
opens a function call, and '}' ends the token. A name carrying one resolves
by dot path and is advertised by List, yet no format can name it.

These pin the rejection, and one accepted case fixes the boundary: ')' on
its own is spellable, so it stays legal.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

bound_test.go

@@ -405,7 +405,7 @@ func TestDottedTokenErrors(t *testing.T) {
 		},
 		"dotted field key": {
 			`{"format":"[{a.b}]","a.b":["V"]}`,
-			`contains a dot`,
+			`contains "."`,
 		},
 	}
 	for name, c := range rejected {