Add the 1.6.0 lint regression test (missed in the release commit staging)

Seeds archive/notes/README.md and asserts vault_lint flags retired-path —
fails against the pre-1.6.0 linter, passes with the retired-first check.

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

eval/test_features.py

@@ -298,6 +298,14 @@ def main():
         check("v1.5 sweep backfills the kind tag",
               "tags: [company]" in drift or '<fm:tags=["company"]>' in drift, drift)
 
+        # 16b. lint blind spot (1.6.0): a seed README inside a retired tree must be
+        # flagged retired-path — previously the permissive leaf-readme route matched
+        # first and absolved it, so retired dirs holding only a README went unflagged.
+        h.seed("archive/notes/README.md", "This folder holds archived notes.\n")
+        r = h.echo(LINT)
+        check("v1.6 lint flags a README inside a retired tree",
+              "archive/notes/README.md: retired location" in r.stdout, r.stdout[-800:])
+
         # 17. hooks: stop-hook nudges once on a substantive session, then stays quiet.
         import tempfile
         tdir = Path(tempfile.mkdtemp())