fix(mcp): project reads list milestones without their plans, and cap done ones (#4045)

enter_project returned every milestone's full plan body. On a project with 39
milestones the handshake came to ~222k characters, 168k of them bodies (110k
from done milestones). That is past what an MCP client accepts as a tool
result, so the call meant to orient a session arrived as a file to page
through. It grows with a project's history, so any long-lived project on any
install gets there.

- brief_milestone_summary (services/milestones.py) trims summary rows to the
  listing fields: id, title, description, status, order_index and progress.
  The plan is get_milestone's job. user_id, project_id and timestamps repeat
  what the caller knows.
- enter_project and get_project share one block: every open milestone plus
  the 5 most recently updated done ones, in order. milestone_summary_omitted
  is attached only when older done ones were left out, and names
  list_milestones and get_milestone.
- list_milestones lists every milestone, done included, without bodies. It is
  the call the omitted line points to, and it had the same size problem.
- The REST project summary is unchanged; the web UI reads it.

Tests: trimming, the done cap and its order, the omitted key present and
absent, get_project and list_milestones, and a size ceiling on enter_project's
milestone block for a 200-milestone history.

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

tests/test_mcp_tool_projects.py

@@ -71,7 +71,7 @@ async def test_list_projects_wraps_in_dict():
 @pytest.mark.asyncio
 async def test_get_project_enriches_with_milestone_summary():
     p = fake_project(id=5, title="found")
-    milestone_summary = [{"id": 10, "title": "MS", "task_count": 3}]
+    milestone_summary = [{"id": 10, "title": "MS", "status": "active", "total": 3}]
     applicable_payload = {
         "rules": [], "truncated": False, "subscribed_rulebooks": [],
     }
@@ -175,7 +175,7 @@ async def test_enter_project_composes_full_context():
         "truncated": False,
         "subscribed_rulebooks": [{"id": 2, "title": "rb"}],
     }
-    milestone_summary = [{"id": 10, "title": "MS", "task_count": 3}]
+    milestone_summary = [{"id": 10, "title": "MS", "status": "active", "total": 3}]
 
     task1 = MagicMock()
     task1.id = 100; task1.title = "T1"; task1.status = "in_progress"