The inverted view used thread presence as a proxy for self time. This missed self samples on C-level wrapper frames like _run_code, where the node's thread always appears in its children too. Those samples were silently dropped, causing the chart to render narrower than full width. Now uses the explicit self field on each node instead of the thread heuristic.

CC: @pablogsal @lkollar

The issue:

Fix inverted flamegraph width — Currently shows narrow chart when leaves sum to small percentage, wasting screen space

• Issue: Implement PEP 799 – A dedicated profiling package for organizing Python profiling tools #138122

• Issue: Improve Tachyon UX #142927