NodeId Paste/Import Benchmark Plan

Goal

Add a dedicated editor-perf benchmark lane that measures the real withNodeId insert path under paste/import-style fragment insertion.

Why

init-dissection only measures initialization and static normalization. It does not exercise the hot insert_node work inside withNodeId, so it cannot tell us whether more paste/import surgery is worth it.

Steps

1. Add a NodeId fragment benchmark type to the editor-perf harness.
2. Measure real insertFragment work against NodeId modes that matter.
3. Separate raw-import and seeded-paste fragment cases.
4. Record the same counters that matter for NodeId cost:
   • ids assigned
   • duplicate lookup count/time
   • inserted node count
5. Verify the harness with targeted checks and one live run.