chore: trigger the site only on its own inputs

The site deploy still triggered on seven scripts it stopped importing
when the pack and site modules were split, and on the test suite it
never runs, so a builder-only push rebuilt the site for nothing. The
triggers now match the build's import closure in both directions.

tests/test_workflow_paths.py

@@ -84,6 +84,12 @@ class DeploySiteTriggers(unittest.TestCase):
             if not any(fnmatch.fnmatch(path, p.replace("**", "*")) for p in patterns)
         )
         self.assertEqual(uncovered, [])
+        # And no script the build no longer reaches: generate_pack.py and six
+        # others stayed listed after the site stopped importing the builder,
+        # and a push touching only them rebuilt the site for nothing.
+        listed = {p for p in patterns if p.startswith("scripts/") and p.endswith(".py")}
+        self.assertEqual(sorted(listed - closure(entry_points)), [])
+        self.assertNotIn("tests/**", patterns)
 
 
 class DocumentedSteps(unittest.TestCase):