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/agent/mcp/test_device_tools.py

@@ -246,7 +246,9 @@ class TestDuplicateDeviceMerging:
         nornir = MagicMock()
         nornir.run.return_value = _aggregated_result({"R1": "merged output"})
         with (
-            patch(f"{CONFIG_MOD}.get_device_ports_from_topology", return_value={"R1": {"port": 5000, "node_type": "iou"}}),
+            patch(
+                f"{CONFIG_MOD}.get_device_ports_from_topology", return_value={"R1": {"port": 5000, "node_type": "iou"}}
+            ),
             patch.object(ExecuteMultipleDeviceConfigCommands, "_initialize_nornir", return_value=nornir),
         ):
             result = ExecuteMultipleDeviceConfigCommands()._run(
@@ -310,7 +312,9 @@ class TestDuplicateDeviceMerging:
         nornir = MagicMock()
         nornir.run.return_value = _aggregated_result({"R1": "ok"})
         with (
-            patch(f"{DISPLAY_MOD}.get_device_ports_from_topology", return_value={"R1": {"port": 5000, "node_type": "iou"}}),
+            patch(
+                f"{DISPLAY_MOD}.get_device_ports_from_topology", return_value={"R1": {"port": 5000, "node_type": "iou"}}
+            ),
             patch.object(ExecuteMultipleDeviceCommands, "_initialize_nornir", return_value=nornir),
             patch(f"{DISPLAY_MOD}.filter_forbidden_commands", side_effect=fake_filter),
         ):

tests/agent/mcp/test_locators.py

@@ -69,8 +69,12 @@ def test_uuid_params_pass_through_without_calls():
 def test_project_name_resolved():
     """A name-shaped project_id becomes the project's UUID."""
 
-    run, calls = _run_factory(projects=[{"project_id": "11111111-1111-1111-1111-111111111111", "name": "other"},
-                                        {"project_id": PROJECT_ID, "name": "my-lab"}])
+    run, calls = _run_factory(
+        projects=[
+            {"project_id": "11111111-1111-1111-1111-111111111111", "name": "other"},
+            {"project_id": PROJECT_ID, "name": "my-lab"},
+        ]
+    )
     params, error = resolve_locators({"project_id": "my-lab"}, run)
     assert error is None
     assert params["project_id"] == PROJECT_ID
@@ -88,8 +92,9 @@ def test_project_name_not_found_lists_known_names():
 
 def test_node_name_resolved_within_project():
 
-    run, calls = _run_factory(projects=[{"project_id": PROJECT_ID, "name": "my-lab"}],
-                              nodes=[{"node_id": NODE_ID, "name": "FRRDocker-4"}])
+    run, calls = _run_factory(
+        projects=[{"project_id": PROJECT_ID, "name": "my-lab"}], nodes=[{"node_id": NODE_ID, "name": "FRRDocker-4"}]
+    )
     params, error = resolve_locators({"project_id": "my-lab", "node_id": "FRRDocker-4"}, run)
     assert error is None
     assert params["project_id"] == PROJECT_ID
@@ -125,11 +130,10 @@ def test_handler_failure_during_resolution_is_reported():
 def test_did_you_mean_appended_for_transcription_slip():
     """The 2c9e -> 3b9e class of typo earns exactly one hint."""
 
-    run, _calls = _run_factory(projects=[{"project_id": PROJECT_ID, "name": "my-lab"}],
-                               nodes=[{"node_id": NODE_ID, "name": "FRRDocker-4"}])
-    result = add_did_you_mean(
-        {"error": f"Node ID {NODE_ID_TYPO} doesn't exist"}, {"project_id": PROJECT_ID}, run
+    run, _calls = _run_factory(
+        projects=[{"project_id": PROJECT_ID, "name": "my-lab"}], nodes=[{"node_id": NODE_ID, "name": "FRRDocker-4"}]
     )
+    result = add_did_you_mean({"error": f"Node ID {NODE_ID_TYPO} doesn't exist"}, {"project_id": PROJECT_ID}, run)
     assert f"Did you mean node 'FRRDocker-4' ({NODE_ID})" in result["error"]
     # original message preserved
     assert NODE_ID_TYPO in result["error"]
@@ -144,9 +148,7 @@ def test_no_hint_when_too_far_or_ambiguous():
 
     two = [NODE_ID, "b78a2630-2b9e-4b43-9397-c855c8053d1a"]  # both within distance 2 of the typo
     run2, _calls2 = _run_factory(nodes=[{"node_id": i, "name": f"n{i}"} for i in two])
-    result2 = add_did_you_mean(
-        {"error": f"Node ID {NODE_ID_TYPO} doesn't exist"}, {"project_id": PROJECT_ID}, run2
-    )
+    result2 = add_did_you_mean({"error": f"Node ID {NODE_ID_TYPO} doesn't exist"}, {"project_id": PROJECT_ID}, run2)
     assert "Did you mean" not in result2["error"]