Adds two new IPCQ architecture views in the latency_model.png aesthetic:
a 2x2 flow figure (one per case) and a 4x1 stacked figure for taller
horizontal panels. Refactors per-case panel drawing into shared helpers
and disambiguates the flit labels (HMQ desc -> Hd so it does not
collide with data D). Two-row legend keys.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
