Task: Recapture dedicated carousel screenshots

The carousel currently uses whatever composite (multi-window) screenshot from an old release happened to fit each topic: v0.0.24 for org structure, v0.0.12 for reference data, v0.0.15 for compute, v0.0.20 for the shell. These are stand-ins, not purpose-built shots – stale UI chrome/theme from past releases, framing chosen for a different context. Capture fresh, dedicated composite screenshots (several relevant windows arranged together, current UI/theme, current data) for each carousel slide.

• Fresh composite screenshots captured, current UI/theme, for: org structure/hierarchy, reference data, compute grid, and the shell – replacing the four old-release stand-ins (ore_studio-v0.0.24.png, ore_studio-v0.0.12.png, ore_studio-v0.0.15.png, ore_studio-v0.0.20.png).
• New images saved under `assets/images/` with descriptive names, and `index.org`'s carousel slides updated to reference them.
• Consider also recapturing the Cross-Rates Matrix, Market Simulator, and Data Librarian slides at the same time if a cleaner shot is easy to get, though those three are already dedicated/composite shots (not stand-ins) and lower priority than the four above.

(Implementation strategy. Written when work starts; key decisions are distilled into the parent story's * Decisions at close, but the plan itself stays — it is the historical record of what we did.)

Manual QA scenarios (scaffolded via compass add test_scenario, run through the QA Validation Runner panel) that verify this task. Link new ones here as they're created; the scenario doc itself links back via its "Verifies task" field.