fix(tests): the browse vocabulary guard names the fourth kind (#3729)

CI 7016. `test_non_task_facets_are_the_note_types_and_only_those` pins the
non-task vocabulary as a literal set, so adding `lesson` to `_FACETS` turned
it red — the guard working, not breaking. It stays a literal: derived from
_FACETS it would assert nothing, and rule 167 wants a guard that can fail.

The representative corpus had no lesson row, so `lesson` was reaching only
the two tests that iterate FACET_TYPES and never the one that asserts each
facet selects EXACTLY its own rows. It has one now, which is what pins the
half that matters: a lesson is not picked up by the Notes facet despite
both being non-task records.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

tests/test_knowledge_facets.py

@@ -38,6 +38,7 @@ ROWS = {
     "plain note": fake_note(note_type="note"),
     "process": fake_note(note_type="process"),
     "snippet": fake_snippet(),
+    "lesson": fake_note(note_type="lesson"),
     "work task": fake_task(task_kind="work", note_type="note"),
     "issue": fake_task(task_kind="issue", note_type="note"),
     "spike": fake_task(task_kind="spike", note_type="note"),
@@ -72,6 +73,7 @@ def test_pre_filter_never_excludes_a_row_the_facet_wants(facet):
         ("note", {"plain note"}),
         ("process", {"process"}),
         ("snippet", {"snippet"}),
+        ("lesson", {"lesson"}),
         ("", set(ROWS)),
     ],
 )
@@ -101,7 +103,11 @@ def test_the_live_task_kinds_are_all_facets():
 
 
 def test_non_task_facets_are_the_note_types_and_only_those():
-    assert set(NON_TASK_FACETS) == {"note", "process", "snippet"}
+    """Spelled out rather than derived, so adding a kind to `_FACETS` has to
+    be a deliberate edit in two places. `lesson` joined in milestone 385 step
+    2 (#3729) and is non-task on purpose: `is_task` IS `status is not None`,
+    so a lesson that acquired a status would stop being a lesson."""
+    assert set(NON_TASK_FACETS) == {"note", "process", "snippet", "lesson"}
 
 
 @pytest.mark.parametrize("facet", sorted(FACET_TYPES))