fix: repair imports lost in the 3.1 rebase and meet the new lint baseline

The rebase onto upstream 3.1 (mypy + ruff I001/F401 waves) left the tree
short of the newly enforced baselines in three ways:

* contextlib / UbridgeError imports dropped as false duplicates during
  conflict resolution left NameErrors in iou_vm and qemu_vm (F821);
  the Dynamips router grabbed the compute-level NIOTAP instead of the
  hypervisor one, breaking TAP anchoring (test failure).
* unused imports (KERNEL_UNSUPPORTED_FILTERS, UbridgeError, List) and
  unsorted blocks left behind where the stack's later commits moved the
  last usage elsewhere — ruff I001/F401/RUF022 now enforce these.
* mypy, now baseline-free: cache dict annotations in tc_probe, the
  locators candidate list, the resolved-params None branch in the MCP
  runner, and validate_bpf_syntax keeps the upstream Dict[str, Any]
  return (the strict Optional[str] was wrong for the "valid" bool entry).

The e2e raw-frame probe resolves its compiler via shutil.which (S607)
and zips with strict= (B905); the remaining subprocess call is S603 by
nature and gets a per-file ignore like other test files.

ruff check/format clean, mypy at upstream parity (no new errors),
full unit suite 2167 passed.

tests/compute/docker/test_docker_kernel_datapath.py

@@ -23,23 +23,18 @@ fallback and cleanup.
 
 import os
 import uuid
-from unittest.mock import MagicMock, call
+from unittest.mock import MagicMock, call, patch
 
 import pytest
 import pytest_asyncio
 
-from unittest.mock import patch
-
-from tests.utils import AsyncioMagicMock
-
-from gns3server.compute.docker import Docker
-from gns3server.compute.docker.docker_vm import DockerVM
-from gns3server.compute.docker.docker_error import DockerError, DockerHttp404Error
 from gns3server.compute.compute_error import ComputeError
-from gns3server.compute.nios.nio_udp import NIOUDP
+from gns3server.compute.docker import Docker
+from gns3server.compute.docker.docker_error import DockerError, DockerHttp404Error
+from gns3server.compute.docker.docker_vm import DockerVM
 from gns3server.compute.nios.nio_bridge import NIOBridge
 from gns3server.compute.ubridge.ubridge_error import UbridgeError
-
+from tests.utils import AsyncioMagicMock
 
 BRIDGE = "gns3a1b2c3d4e5f"
 
@@ -1373,7 +1368,13 @@ def test_create_nio_udp_rejects_kernel_only_filters(vm):
 
     with pytest.raises(ComputeError, match="kernel-datapath"):
         vm.manager.create_nio(
-            {"type": "nio_udp", "lport": 4242, "rport": 4343, "rhost": "127.0.0.1", "filters": {"gemodel": [100, 0, 30]}}
+            {
+                "type": "nio_udp",
+                "lport": 4242,
+                "rport": 4343,
+                "rhost": "127.0.0.1",
+                "filters": {"gemodel": [100, 0, 30]},
+            }
         )
 
 

tests/compute/docker/test_iol_docker_kernel_datapath.py

@@ -14,19 +14,15 @@ Image-free: everything is asserted against the uBridge command stream and
 the anchor naming contract.
 """
 
-import uuid
+from unittest.mock import MagicMock, patch
 
 import pytest
 import pytest_asyncio
 
-from unittest.mock import MagicMock, patch
-
-from tests.utils import AsyncioMagicMock
-
 from gns3server.compute.docker import Docker
 from gns3server.compute.docker.docker_error import DockerError
 from gns3server.compute.docker.iol_docker_vm import IOLDockerVM
-
+from tests.utils import AsyncioMagicMock
 
 NODE_ID = "00010203-0405-0607-0809-0a0b0c0d0e0f"
 TAP00 = "gx00010203e0p0"  # the vm fixture's node id, bay 0 unit 0
@@ -296,7 +292,9 @@ async def test_remove_nio_binding_kernel_releases_the_port_leg_first(vm):
     commands = _commands(vm)
     assert f"bridge stop {PORT_BRIDGE}" in commands
     assert f'bridge delete_nio_tap {PORT_BRIDGE} "{TAP00}"' in commands
-    assert commands.index(f"bridge stop {PORT_BRIDGE}") < commands.index(f'bridge delete_nio_tap {PORT_BRIDGE} "{TAP00}"')
+    assert commands.index(f"bridge stop {PORT_BRIDGE}") < commands.index(
+        f'bridge delete_nio_tap {PORT_BRIDGE} "{TAP00}"'
+    )
     assert f'tc reset "{TAP00}"' in commands
     assert f'brctl delif "{BRIDGE}" "{TAP00}"' in commands
     assert f'brctl delete "{BRIDGE}"' in commands

tests/compute/docker/test_vendor_docker_vm.py

@@ -908,6 +908,7 @@ async def test_create_reparse_refreshes_env_knobs(compute_project, manager):
 # Kernel-datapath (NIOBridge) rejection
 # ---------------------------------------------------------------------------
 
+
 @pytest.mark.asyncio
 async def test_unix_socket_nio_rejects_kernel_datapath_link(compute_project, manager):