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

src/scribe/mcp/tools/milestones.py

@@ -44,7 +44,10 @@ async def get_milestone(milestone_id: int) -> dict:
     rules surface again on recall.
 
     Returns: milestone (incl. body), progress, steps (its tasks ordered by
-    status then update), and applicable_rules / project_rules.
+    status then update), and applicable_rules / project_rules. Each step says
+    what it is and where it stands, not its whole body — read a step in full
+    with get_task(id). A plan with forty long steps is otherwise too big to
+    arrive inline, and the design is in the milestone body.
     """
     uid = current_user_id()
     milestone = await milestones_svc.get_milestone(uid, milestone_id)
@@ -61,7 +64,7 @@ async def get_milestone(milestone_id: int) -> dict:
     out.update(progress)
     return {
         "milestone": out,
-        "steps": [t.to_dict() for t in steps],
+        "steps": [notes_svc.brief_row(t, {milestone.id: milestone.title}) for t in steps],
         **rulebooks_svc.rules_payload(applicable, user_id=uid, source="get_milestone"),
     }