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.

gns3server/agent/mcp/__init__.py

@@ -346,13 +346,13 @@ def _run_handler_sync(handler, params: dict[str, Any]) -> list[dict[str, Any]]:
 
     # Name-shaped project_id/node_id values become UUIDs before the handler
     # runs; a name that matches nothing fails fast with the known names.
-    params, resolution_error = resolve_locators(params, run)
-    if resolution_error is not None:
+    resolved_params, resolution_error = resolve_locators(params, run)
+    if resolved_params is None:
         result = resolution_error
     else:
-        result = handler(params, ctx)
+        result = handler(resolved_params, ctx)
         # backstop for UUID transcription slips: "Did you mean ...?"
-        result = add_did_you_mean(result, params, run)
+        result = add_did_you_mean(result, resolved_params, run)
     return [{"type": "text", "text": json.dumps(result, ensure_ascii=False, default=str)}]