feat(issues): S2 MCP tools — system CRUD + issue/system wiring

Second slice of Issues + Systems (spec #825).

New mcp/tools/systems.py: create_system, list_systems, get_system (records
split into issues/tasks/notes), update_system (incl. archive via status),
list_system_records (kind/open_only filters), delete_system. Registered in
register_all; read tools (get_system, list_systems, list_system_records) added
to the read-only-key allowlist (write tools default-deny).

create_task/update_task: kind now accepts 'issue'; new system_ids (set-semantics
associations) and arose_from_id (provenance, 0=unchanged/-1=clear) args.
create_note/update_note: new system_ids arg (notes associate with systems too).
services/notes.create_note: arose_from_id passthrough (update_note already
handles it via setattr).

Tests: MCP system tools + create_task issue-wiring (kind/provenance/systems),
service layer mocked.

Refs plan 825 (S2).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_mcp_tool_systems.py

@@ -0,0 +1,75 @@
+"""MCP system tools + task/note issue wiring (service layer mocked)."""
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+
+
+def _fake_system(sid=1, name="Reader", project_id=5):
+    s = MagicMock()
+    s.to_dict.return_value = {"id": sid, "name": name, "project_id": project_id}
+    s.project_id = project_id
+    return s
+
+
+@pytest.mark.asyncio
+async def test_create_system_returns_dict():
+    with patch("scribe.mcp.tools.systems.current_user_id", return_value=1), \
+         patch("scribe.mcp.tools.systems.systems_svc") as svc:
+        svc.create_system = AsyncMock(return_value=_fake_system(name="Reader"))
+        from scribe.mcp.tools.systems import create_system
+        result = await create_system(project_id=5, name="Reader", description="pdf reader")
+    assert result["name"] == "Reader"
+
+
+@pytest.mark.asyncio
+async def test_create_system_no_access_raises():
+    with patch("scribe.mcp.tools.systems.current_user_id", return_value=1), \
+         patch("scribe.mcp.tools.systems.systems_svc") as svc:
+        svc.create_system = AsyncMock(return_value=None)
+        from scribe.mcp.tools.systems import create_system
+        with pytest.raises(ValueError):
+            await create_system(project_id=5, name="Reader")
+
+
+@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
+    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(sid=3))
+        svc.list_records_for_system = AsyncMock(return_value=[issue, work, note])
+        from scribe.mcp.tools.systems import get_system
+        result = await get_system(system_id=3)
+    assert [r["id"] for r in result["issues"]] == [10]
+    assert [r["id"] for r in result["tasks"]] == [11]
+    assert [r["id"] for r in result["notes"]] == [12]
+
+
+@pytest.mark.asyncio
+async def test_update_system_not_found_raises():
+    with patch("scribe.mcp.tools.systems.current_user_id", return_value=1), \
+         patch("scribe.mcp.tools.systems.systems_svc") as svc:
+        svc.update_system = AsyncMock(return_value=None)
+        from scribe.mcp.tools.systems import update_system
+        with pytest.raises(ValueError):
+            await update_system(system_id=99, name="x")
+
+
+@pytest.mark.asyncio
+async def test_create_task_issue_sets_kind_provenance_and_systems():
+    note = MagicMock(); note.id = 50; note.to_dict.return_value = {"id": 50, "task_kind": "issue"}
+    with patch("scribe.mcp.tools.tasks.current_user_id", return_value=1), \
+         patch("scribe.mcp.tools.tasks.notes_svc") as notes_svc, \
+         patch("scribe.mcp.tools.tasks.systems_svc") as systems_svc:
+        notes_svc.create_note = AsyncMock(return_value=note)
+        systems_svc.set_record_systems = AsyncMock(return_value=[2, 3])
+        systems_svc.list_record_systems = AsyncMock(return_value=[])
+        from scribe.mcp.tools.tasks import create_task
+        result = await create_task(title="bug", kind="issue", system_ids=[2, 3], arose_from_id=9)
+    _, kwargs = notes_svc.create_note.call_args
+    assert kwargs["task_kind"] == "issue"
+    assert kwargs["arose_from_id"] == 9
+    systems_svc.set_record_systems.assert_awaited_once_with(1, 50, [2, 3])
+    assert result["id"] == 50