docs(6209): preference door, systems and notes tools, lesson surfacing, rule versions, backup round trip, JSON reader, charter search, provenance, location filter

Ten more test files: issue, milestone, rule, decision and snippet numbers
come out of docstrings, comments and messages; the preference door states
what a preference is instead of quoting the framing; the JSON reader says
why jq is not assumed instead of what every hook used to do; the backup
round trip's column warning no longer claims the import side is unguarded.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_system_charter_search.py

@@ -1,4 +1,4 @@
-"""Systems become findable by meaning — the charter as an ANSWER (#4251).
+"""Systems become findable by meaning — the charter as an ANSWER.
 
 A System's `description` is a charter: several hundred words saying what
 belongs in that area and what does not. It is the answer to "where does this
@@ -20,7 +20,7 @@ from tests.helpers import make_mock_session
 
 def _system(system_id=3, name="Retrieval & recall", description="the charter"):
     s = MagicMock(id=system_id, project_id=2, description=description)
-    s.name = name          # never via the constructor — see note #2833
+    s.name = name          # never via the constructor: `name` names the mock
     return s
 
 
@@ -65,8 +65,7 @@ def _rows_ctx(rows):
 async def test_the_search_collapses_to_best_chunk_and_reports_which_one_won():
     """A charter is long, and a result shows its NAME — so the paragraph that
     actually decides where a record belongs has to come back with it, or the
-    caller judges from two words that cannot say (#4243). Published from the
-    start here rather than retrofitted, which is what #4251 asked for."""
+    caller judges from two words that cannot say."""
     a, b = _system(3), _system(4, name="Data Model")
     rows = [
         (a, 0.10, 2, "retrieval telemetry belongs here"),
@@ -94,7 +93,7 @@ async def test_the_search_collapses_to_best_chunk_and_reports_which_one_won():
 
 @pytest.mark.asyncio
 async def test_a_project_the_caller_cannot_read_returns_nothing():
-    """Rule 78 — the charter of a project someone was not given is not an
+    """The charter of a project someone was not given is not an
     answer to any question they are entitled to ask."""
     _session, ctx = _rows_ctx([])
     with (