fix(gb-core): default CGB to CPU-CGB-D

[pakitovic]

Summary

• Change the ordinary Game Boy Color default revision from CpuCgbE to CpuCgbD.
• Keep CGB-E as an explicit active revision and preserve the existing boot ROM asset mapping: CpuCgbD -> cgb_boot.bin, CpuCgbE -> cgbE_boot.bin.
• Update CLI, desktop, test-runner expectations, and model/boot documentation for the new default without pinning implicit CGB manifests to CGB-E.

Validation

• cargo fmt --all -- --check
• git diff --check
• cargo test -p gb-core --test model --test boot --test bus
• cargo test -p gb-cli
• cargo test -p gb-desktop
• cargo test -p gb-test-runner
• cargo rom-suite gb-emulator-shootout --suite samesuite-apu (61/61 passed)
• RealBoot smoke check with a temporary boot ROM directory containing only cgb_boot.bin for an implicit CGB case