feat(mcp): assemble the 8-tool toolkit with capability gating, proven via real dispatch

Also fixes async-test DB isolation: test_mcp_toolkit.py drives real MCP
dispatch, which runs tool functions' ORM calls on a sync_to_async worker
thread outside pytest-django's per-test atomic transaction, so writes
committed there weren't rolled back and leaked into later tests. Sets
DJANGO_ALLOW_ASYNC_UNSAFE for the async ORM setup calls and flushes the
Printer table after this file's tests via conftest.py.

tests/test_mcp_toolkit.py

@@ -0,0 +1,83 @@
+"""Proves this toolkit's capability assignments are wired correctly through
+real MCP dispatch -- not by calling tool functions directly. See
+~/src/mcp-gate/tests/test_end_to_end.py for the pattern this is modeled on;
+mcp-gate's own HTTP-shaped dispatch machinery is already tested there, so
+this file only needs the stdio-shaped Client, which is enough to drive
+server.middleware and prove which tools this toolkit's capability tags
+actually gate.
+"""
+import pytest
+from mcp.client import Client
+from mcp.shared.exceptions import MCPError
+
+from mcp_gate import Gate, OpenIdentity
+
+from bambu_run.mcp.toolkit import build_toolkit
+from bambu_run.models import Printer
+
+pytestmark = pytest.mark.anyio
+
+
+@pytest.fixture
+def anyio_backend():
+    return "asyncio"
+
+
+async def test_full_capability_caller_sees_all_eight_tools(db):
+    Printer.objects.create(name="RNL-H2C", model="H2C", is_active=True)
+    gate = Gate(
+        name="test",
+        toolkits=[build_toolkit()],
+        identity=OpenIdentity(["read_printer", "read_print_history", "read_filament"]),
+    )
+    server = gate.build_server()
+
+    async with Client(server, mode="legacy") as client:
+        result = await client.list_tools()
+
+    names = {t.name for t in result.tools}
+    assert names == {
+        "get_printer_status", "get_metrics_history", "get_hardware_health",
+        "list_print_jobs", "get_print_job", "get_print_statistics",
+        "list_filaments", "get_filament",
+    }
+
+
+async def test_read_printer_only_caller_cannot_see_or_call_filament_tool(db):
+    Printer.objects.create(name="RNL-H2C", model="H2C", is_active=True)
+    gate = Gate(
+        name="test",
+        toolkits=[build_toolkit()],
+        identity=OpenIdentity(["read_printer"]),
+    )
+    server = gate.build_server()
+
+    async with Client(server, mode="legacy") as client:
+        visible = await client.list_tools()
+        visible_names = {t.name for t in visible.tools}
+        assert "list_filaments" not in visible_names
+        assert "get_printer_status" in visible_names
+
+        with pytest.raises(MCPError):
+            await client.call_tool("list_filaments", {})
+
+
+async def test_read_printer_caller_can_call_get_printer_status(db):
+    Printer.objects.create(name="RNL-H2C", model="H2C", is_active=True)
+    gate = Gate(
+        name="test",
+        toolkits=[build_toolkit()],
+        identity=OpenIdentity(["read_printer"]),
+    )
+    server = gate.build_server()
+
+    async with Client(server, mode="legacy") as client:
+        result = await client.call_tool("get_printer_status", {})
+        assert result is not None
+
+
+def test_build_toolkit_has_no_name_collisions():
+    # Toolkit.tool() raises ValueError on a name collision at registration
+    # time -- building it twice without raising is itself the assertion.
+    build_toolkit()
+    build_toolkit()