Binder gaps left by the notebook E2E (#26) #172

From ksp-fixtures/notebook-e2e README 'Gaps' and pythonx-compose's review (2026-10-04). Each becomes its own issue in its turn.

• Run :ksp-fixtures:notebook-e2e in CI (needs the pythonx-compose wheel as an input; today the evidence is one local run, 20/20 on 2026-10-04).
• Button/Card corner_radius and colour: Kotlin takes shape= / colors=; androidx.compose.foundation.shape is not walked, and ButtonDefaults.buttonColors is declined by the walker (B-1).
• Card(modifier=Modifier): a proxy class passed as an argument.
• Colour-scheme factories (pythonx-compose SPEC S5.3) blocked by the omission cap.
• AWT IME decoding layer (needs a window), not covered by the scene-level IME test.