[fine] Ignore tests sometimes

fine/tests/README.md

@@ -37,6 +37,8 @@ e.g., a test might look like this:
 
 The various assertions are as follows:
 
+- The `// @disabled` directive marks the test as ignored.
+
 - The `// @concrete:` assertion says that the following lines
   (prefixed with `// | `, as above) describe the concrete syntax tree
   of the file after parsing.

fine/tests/expression/empty_statement.fine

@@ -0,0 +1,5 @@
+// @disabled
+// @concrete:
+// |
+
+;