refactor(bb.js): migrate to ipc-codegen + ipc-runtime; delete legacy bb::ipc

[charlielye]

Summary

Migrates bb.js and the remaining NAPI IPC substrate to the shared runtime, then removes the legacy bb::ipc transport.

This is the final bb-side migration PR before the AVM/wsdb cutover PRs.

Stack

1. feat(ipc): add /ipc-codegen and /ipc-runtime foundation packages #23610 cl/ipc-foundation
2. refactor(wsdb): migrate aztec-wsdb to ipc-codegen + ipc-runtime #23611 cl/ipc-wsdb-migrate
3. refactor(bbapi): migrate bb binary to ipc-codegen + ipc-runtime #23612 cl/ipc-bb-migrate
4. refactor(barretenberg-rs): migrate to ipc-codegen + ipc-runtime; drop PipeBackend #23613 cl/ipc-bb-rs-migrate
5. refactor(bb.js): migrate to ipc-codegen + ipc-runtime; delete legacy bb::ipc #23614 cl/ipc-bb-js-migrate — this PR
6. refactor: cut-over to new wsdb package - comms over uds ipc. #23036 cl/ipc-3-avm-wsdb-cutover
7. feat: add generated aztec-vm-sim package setup #23084 cl/ipc-4-avm-binary
8. feat: cut simulator over to generated bb-avm-sim IPC service #23697 cl/ipc-5-avm-cutover

What changes

• bb.js UDS clients use @aztec/ipc-runtime instead of local hand-written socket code.
• bb.js SHM clients use @aztec/ipc-runtime NAPI SHM bindings instead of the old NAPI msgpack client wrapper.
• Removes the redundant nodejs_module/msgpack_client C++ wrapper/async client implementation.
• Removes the legacy barretenberg/cpp/src/barretenberg/ipc/ library once all consumers have moved to ipc_runtime.
• Keeps generated bb API error handling compatible with BBApiException.
• Keeps bb.js package binary resolution on the arch-package model introduced in refactor(bbapi): migrate bb binary to ipc-codegen + ipc-runtime #23612.

End state after this PR

• bb and wsdb servers use codegen-emitted handlers over ipc_runtime.
• bb.js and barretenberg-rs use generated typed clients over shared runtime transports.
• The legacy bb::ipc implementation is gone.

Validation

• barretenberg/ts ESM/CJS build.
• Root ./bootstrap.sh passed on this branch during stack validation after cleaning stale local CMake state that had cached AVM=OFF.

[charlielye]

Superseded by #25362, which lands this work off next as one PR. Envelope ids (the 8-byte request-id frame prefix) landed after these were opened and broke wire compatibility between the old and new stacks, so bb, bb.js and bb-rs have to migrate together and can no longer go in independently. This PR was used as the recipe for it.