fix(state): serialize CPU dataBus and controller state

[SergioChan]

Summary

• add dataBus to CPU.JSON_PROPERTIES so open-bus state survives save/load
• serialize/restore controller runtime state in NES.toJSON() / NES.fromJSON()
• add regression test covering dataBus and controller state round-trip

Testing

• npm run typecheck
• node --test ./test/nes.spec.js --test-name-pattern "serializes CPU dataBus and controller state"

Related

Fixes #614

[bfirsh]

Thanks for the contribution! The build is failing.

[SergioChan]

Thanks for flagging this — you were right. The CI failure came from missing controller.d.ts declarations for the new toJSON/fromJSON methods and JSON_PROPERTIES static member.

I just pushed a follow-up commit (fix(types): declare controller JSON serialization members) to this PR branch, and re-ran the relevant tests locally:

• node --test test/typedefs.spec.js
• node --test test/nes.spec.js

Both pass now.