feat: Godspeed Lite — SOTA benchmark infrastructure + minimal coding agent

[t-timms]

Summary

Adds comprehensive benchmark infrastructure and Godspeed Lite, a minimal ~480-line coding agent optimized for SWE-bench performance. Synthesizes architecture learnings from Amp, Factory, PI, Claude Code, and mini-SWE-agent v2.

What's included

Benchmark Infrastructure

• SOTA Audit — 12-benchmark competitive analysis vs 6 competitor harnesses (Amp, Factory, PI, Claude Code, Cursor, mini-SWE-agent). Maps Godspeed position across security, cost, and score dimensions.
• Benchmark Plan — 6 SOTA targets, prioritized run order, cost estimates, reliability architecture, 14 research references.
• NIM Key Rotation — 4-key manager with RPM tracking, 429 cooldown with exponential backoff, env var integration. 17 tests passing.
• Pre-flight Checker — Validates NIM auth, Docker, WSL, disk space, Python env before benchmark runs.
• SWE-bench Runner — Predictions generator with heartbeat logging, crash-resume checkpointing, per-instance timeout enforcement, failure forensics.

Godspeed Lite Agent

• Bash-only agent loop — 480 lines, subprocess.run, linear history, no permissions, no async dispatch
• 3 modes — smart (Opus-class), rush (15-step fast), deep (60-step thorough + model roulette)
• Model roulette — Random driver model swap per step (free 3-8% benchmark boost per mini-SWE-agent blog)
• AGENTS.md loading — Amp-style project context auto-detection
• Auto test detection — Infers pytest/jest/cargo/go test commands from project files
• Single-shot fallback — 1-call mode for rate-constrained free tier
• 29 tests passing, 0 lint errors

Verification

uv run pytest tests/test_nim_key_rotation.py tests/test_godspeed_lite.py  # 46 passed
uv run ruff check src/godspeed/lite/ src/godspeed/benchmarks/            # 0 errors

Commands

godspeed-lite "fix bug"                          # smart mode (default)
godspeed-lite --mode rush "add docstring"        # fast mode
godspeed-lite --mode deep "debug race condition" # thorough mode
godspeed-lite --single-shot "fix the IndexError" # 1-call mode