feat: Consolidated SDK with Rust-compatible builder API and FFI bindings

[Mikerah]

Summary

Consolidated Python SDK implementation with:

• Rust SDK-compatible builder API (Stoffel.compile().parties(5).threshold(1).build())
• Complete FFI bindings ported from closed PRs feat(vm): Implement VM bytecode loading and execution via ctypes #3 and feat(mpc): Update secret sharing FFI bindings #4
• Working local execution via native VM
• NEW: MPC-as-a-Service (MPCaaS) server with HoneyBadger protocol support
• NEW: Party ID support for correct MPC share distribution

Changes

New High-Level API

• Stoffel entry point with compile(), compile_file(), load() methods
• StoffelBuilder fluent builder for MPC configuration
• StoffelRuntime thin wrapper holding program + config
• MPCConfig dataclass matching Rust SDK
• ProtocolType, ShareType, OptimizationLevel enums
• Unified error hierarchy (StoffelError, CompilationError, ConfigurationError, etc.)

FFI Bindings (ported from PRs #3 and #4)

• stoffel/native/vm.py: NativeVM with load() method
• stoffel/native/compiler.py: stoffel_compile_to_binary() FFI
• stoffel/native/mpc.py: Complete MPC FFI with U256, FieldKind, NativeShareManager
• stoffel/_core.py: Working execute_local() implementation

MPCaaS Server (new)

• stoffel/mpcaas/server.py: HoneyBadger MPC server with QUIC networking
• stoffel/native/network.py: QUIC network FFI bindings with party ID support
• stoffel/native/quic_ffi.py: Low-level QUIC FFI including new_quic_network_with_party_id()

MPC Configuration Validation

• Validates HoneyBadger constraint: n >= 3t + 1
• Validates ROBUST shares required for HoneyBadger

Supersedes

• Closes feat(vm): Implement VM bytecode loading and execution via ctypes #3 (feature/vm-bytecode-execution)
• Closes feat(mpc): Update secret sharing FFI bindings #4 (feature/mpc-protocols-ffi)

Dependencies

• Requires mpc-protocols PR #65 for new_quic_network_with_party_id() FFI function

Test plan

• 39 unit tests for builder pattern and config validation
• All existing tests pass
• Manual verification with native libraries
• Integration test with HoneyBadger MPC preprocessing

Usage

from stoffel import Stoffel, ProtocolType, ShareType

runtime = Stoffel.compile("fn main() { return 42; }") \
    .parties(5) \
    .threshold(1) \
    .protocol(ProtocolType.HONEYBADGER) \
    .share_type(ShareType.ROBUST) \
    .build()

print(runtime.program)      # bytes
print(runtime.mpc_config)   # MPCConfig(parties=5, threshold=1, ...)

🤖 Generated with Claude Code