feat(systems): evidence-carrying bootstrap ask for mature zero-Systems projects (#2683)

The generic zero-state systems_hint never converts: identical on every
record, maximal in scope, asked at wrap-up time — Minstrel reached 282
records with zero Systems while vocabularied projects grew organically.
What converts is the project's own evidence at the moment of action.

bootstrap_systems_ask (mcp/tools/systems.py) fires only in a project
with >=20 records and no Systems: it names the record count and recent
titles, and asks for a concrete deliverable — propose 3-6 Systems,
confirm with the operator, create_system the set. Self-retiring: the
first System ends it everywhere. Wired at both moments the task named:
untagged_systems_hint escalates to it at write time, and enter_project
carries it as systems_bootstrap at arrival (attached only when it
applies). Young projects keep the mild question; populated vocabularies
never pay the count query.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_mcp_tool_projects.py

@@ -40,6 +40,18 @@ def _no_coverage():
         yield
 
 
+@pytest.fixture(autouse=True)
+def _no_bootstrap():
+    """With _no_systems stubbing an empty vocabulary, every test here reaches
+    the zero-Systems branch, whose bootstrap ask (#2683) counts the project's
+    records — a database read. Stub the common case (young project, no ask);
+    the firing shape has its own test below.
+    """
+    with patch("scribe.mcp.tools.projects.systems_tools.bootstrap_systems_ask",
+               AsyncMock(return_value=None)) as mock:
+        yield mock
+
+
 def _fake_project(design_system_id=None, **overrides) -> MagicMock:
     p = MagicMock()
     base = {"id": 1, "title": "P", "description": "", "goal": "",
@@ -211,6 +223,9 @@ async def test_enter_project_composes_full_context():
     # vocabulary, and "this project has no named areas yet" is information the
     # create-the-System instruction acts on.
     assert out["systems"] == []
+    # Young project, no bootstrap ask -> the key is ABSENT, not null: it exists
+    # to be acted on, and a key that usually says null gets skipped (#2483).
+    assert "systems_bootstrap" not in out
 
 
 @pytest.mark.asyncio
@@ -251,6 +266,62 @@ async def test_enter_project_surfaces_the_systems_vocabulary():
     ]
 
 
+def _enter_project_stubs(p):
+    """The four patches every enter_project test repeats, as one context list."""
+    return [
+        patch("scribe.mcp.tools.projects.projects_svc.get_project",
+              AsyncMock(return_value=p)),
+        patch("scribe.mcp.tools.projects.rulebooks_svc.get_applicable_rules",
+              AsyncMock(return_value={"rules": [], "truncated": False,
+                                      "subscribed_rulebooks": []})),
+        patch("scribe.mcp.tools.projects.milestones_svc.get_project_milestone_summary",
+              AsyncMock(return_value=[])),
+        patch("scribe.mcp.tools.projects.notes_svc.list_notes",
+              AsyncMock(side_effect=[([], 0), ([], 0)])),
+    ]
+
+
+@pytest.mark.asyncio
+async def test_enter_project_carries_the_bootstrap_ask_when_it_fires():
+    """The arrival-moment half of #2683: a mature zero-Systems project greets
+    the session with the concrete bootstrap ask, before it is deep in a task —
+    the moment "propose a starter vocabulary" is cheapest."""
+    import contextlib
+
+    ask = "This project has 282 records and NO Systems modelled — ..."
+    with contextlib.ExitStack() as stack:
+        for cm in _enter_project_stubs(_fake_project(id=5)):
+            stack.enter_context(cm)
+        stack.enter_context(patch(
+            "scribe.mcp.tools.projects.systems_tools.bootstrap_systems_ask",
+            AsyncMock(return_value=ask),
+        ))
+        out = await enter_project(project_id=5)
+    assert out["systems_bootstrap"] == ask
+
+
+@pytest.mark.asyncio
+async def test_enter_project_never_asks_bootstrap_once_a_vocabulary_exists(
+    _no_bootstrap,
+):
+    """The ask is self-retiring: the first System ends it — enter_project must
+    not even evaluate it once the vocabulary is non-empty."""
+    import contextlib
+
+    sys1 = MagicMock()
+    sys1.id = 3; sys1.name = "retrieval"; sys1.description = ""
+    with contextlib.ExitStack() as stack:
+        for cm in _enter_project_stubs(_fake_project(id=5)):
+            stack.enter_context(cm)
+        stack.enter_context(patch(
+            "scribe.mcp.tools.projects.systems_svc.list_systems",
+            AsyncMock(return_value=[sys1]),
+        ))
+        out = await enter_project(project_id=5)
+    assert "systems_bootstrap" not in out
+    _no_bootstrap.assert_not_awaited()
+
+
 @pytest.mark.asyncio
 async def test_enter_project_hands_back_the_design_system_when_the_project_has_one():
     """The handshake is where an agent learns what binds it, and a design