docs: sample GRPO reward log + curve, human README section, plot colors

feat(ui): DriftShield /play HumanAgent + State observer console

feat(space): enable OpenEnv /web play UI, root redirect, docs and sample rewards CSV

feat(colab): A100 30min preset, vLLM logprobs TRL patch, full reward heads (sid-rp-style)

Improve GRPO prompts for tool-call rewards

Expand Colab preset tasks to target episodes

Add Colab GRPO memory presets

Tune Colab GRPO defaults for 22GB GPUs

Match TRL reward function keyword API

Handle OpenEnv validation errors in GRPO

Harden GRPO rollout action parsing

Fix DriftShield Colab GRPO reward logging

fix(client): reject hub page URL for WebSocket base_url

fix(server): add GET / and favicon 204 for HF Space probes

DriftShield OpenEnv: grader, server, Docker Space, notebooks