ci: point eval at the checkout and keep DevOps in the corpus.

/tmp/brain-eval cannot walk up to var/kb.lbug; KB_ROOT is required.
Recall fragments must exist in README/docs so a repo-only rebuild gates.

bin/tools/test_bin_layout.py

@@ -213,6 +213,19 @@ class BinLayoutTest(unittest.TestCase):
         self.assertIn("bin/brain/eval.go", ci)
         self.assertIn("system_ladybug,brain_eval", ci)
         self.assertIn("/tmp/brain-eval", ci)
+        self.assertIn("KB_ROOT", ci)
         self.assertNotIn("bin/kb/eval", ci)
         self.assertNotIn("gate skipped", ci)
         self.assertIn("./bin/facts/audit self", ci)
+
+    def test_eval_fragments_live_in_default_corpus(self) -> None:
+        """CI --rebuild indexes README/PLAN/docs/skills; fragments must be there."""
+        corpus = []
+        for rel in ("README.md", "PLAN.md", "AGENTS.md"):
+            corpus.append((ROOT / rel).read_text())
+        for d in ("docs", "skills"):
+            for p in (ROOT / d).rglob("*.md"):
+                corpus.append(p.read_text())
+        blob = "\n".join(corpus)
+        for frag in ("BM25", "DevOps", "LadybugDB"):
+            self.assertIn(frag, blob, f"{frag} must appear in default index corpus")