fix(mcp): list tools return rows that say what a record is, not what it says (#4061)

list_tasks returned every row's to_dict(), body included: a project's todo list
came to 93-165k characters, past what an MCP client accepts inline, so the list
arrived as a file to page through (the #4045 failure, one call over).

- notes.brief_row: id, title, type, project, tags, updated_at; for tasks,
  status, kind, priority, milestone id and title; description, parent and due
  date only when set.
- milestones.titles_for: one query for the milestone titles a page of rows
  names.
- Brief rows on list_tasks, list_notes, get_milestone's steps, get_system and
  list_system_records. get_task / get_note / get_snippet read a record in full,
  and each docstring says so.
- tests/test_list_rows_brief.py pins the ceiling: 100 rows of ~5k-character
  step plans stay under 40k characters.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

tests/test_mcp_tool_systems.py

@@ -2,7 +2,7 @@
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
-from tests.helpers import fake_note, fake_system
+from tests.helpers import fake_note, fake_system, fake_task
 
 
 # The name assessment both doors run before minting (milestone 307). A test
@@ -87,9 +87,9 @@ async def test_create_system_duplicate_names_the_existing_one_and_creates_nothin
 
 @pytest.mark.asyncio
 async def test_get_system_splits_records_by_kind():
-    issue = MagicMock(); issue.to_dict.return_value = {"id": 10}; issue.task_kind = "issue"; issue.status = "todo"
-    work = MagicMock(); work.to_dict.return_value = {"id": 11}; work.task_kind = "work"; work.status = "todo"
-    note = MagicMock(); note.to_dict.return_value = {"id": 12}; note.task_kind = "work"; note.status = None
+    issue = fake_task(id=10, task_kind="issue", milestone_id=None)
+    work = fake_task(id=11, milestone_id=None)
+    note = fake_note(id=12, status=None, milestone_id=None)
     with patch("scribe.mcp.tools.systems.current_user_id", return_value=1), \
          patch("scribe.mcp.tools.systems.systems_svc") as svc:
         svc.get_system = AsyncMock(return_value=fake_system(id=3))