feat(shm): Zero-Copy SHM Transport & Remote SkyRL Integration

[RUFFY-369]

PR Type

• RL Environment PR - Complete Environment Snapshot & Zero-Training sections
• Non-Environment PR - Complete Description, Related Issues & Type of Change sections

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📝 General Information

Description

This PR introduces a major architectural enhancement to the Atropos environment ecosystem: a Zero-Copy Shared Memory (SHM) transport backplane.

While this work was primarily driven by the need for high-speed SkyRL integration, the SHM transport is implemented as a generic, opt-in feature in BaseEnv. This allows any Atropos environment to bypass the traditional HTTP/JSON "serialization tax," which has historically limited per-node throughput to ~2k trajectories per second (benchmarked on RTX 3090 cluster).

Key Technical Changes:

• General Purpose SHM Buffer: Implemented ZeroCopySHMBuffer as a core utility. It utilizes multiprocessing.shared_memory and numpy views to enable near-instantaneous transmission of trajectories, scores, and metadata across local-node processes.
• SkyRL Orchestration: Provides the technical foundation for the corresponding SkyRL PR: feat: native Atropos-SHM integration and modular ingestion layer NovaSky-AI/SkyRL#1473 . This includes native support for reasoning-dense traces (Thinking Traces + PRM) and synchronized Task ID tracking.
• Atomic Pointer Safety: Refined index management (read_idx, write_idx) to ensure 100% data integrity during high-concurrency collection (e.g., 4+ environment workers writing to a single trainer).
• BaseEnv Integration: Added native support for SHM transport at the root environment level. Environments can now opt-in to binary-level streaming, bypassing the aiohttp stack entirely.

Performance Benchmarks:

Hardware: 2x RTX 3090
Baseline (HTTP/JSON): ~2,000 traj/s
Zero-Copy SHM: 37,848 traj/s (~19x improvement)
Micro-bench (Latency): 0.10ms (SHM) vs 237ms (JSON)
Integrity: Verified 100% metadata/logprob retention across 1M samples.

Related Issues

Solves issue #439

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Code refactor (no functional changes)
• Build/CI/CD related changes
• Other (please describe):

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✅ Developer & Reviewer Checklist

• Code follows project style (black, isort, flake8 pass with pre-commit)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes
• Docstrings added for all new public classes / functions
• If .env vars required, did you add it to the .env.example in repo root?