feat: make tinker-atropos RL training fully optional

The tinker-atropos submodule and its heavy dependencies (atroposlib, tinker,
wandb, fastapi, uvicorn) were being installed for all users by default,
adding significant install time and disk usage for most users who don't
need RL training capabilities.

Changes:
- install.sh: Only init mini-swe-agent submodule by default; skip
  tinker-atropos clone and install entirely
- install.sh: Remove --recurse-submodules from git clone (only fetches
  what's needed)
- pyproject.toml: Add [rl] optional dependency group for explicit opt-in
- rl_training_tool.py: Move LOGS_DIR.mkdir() from module-level to lazy
  init (_ensure_logs_dir) to avoid side effects on import
- README.md: Update contributor quick start to not auto-fetch
  tinker-atropos; add RL opt-in instructions

Users who want RL training can opt in with:
  git submodule update --init tinker-atropos
  uv pip install -e ./tinker-atropos

README.md

@@ -124,8 +124,9 @@ We welcome contributions! See the [Contributing Guide](https://hermes-agent.nous
 Quick start for contributors:
 
 ```bash
-git clone --recurse-submodules https://github.com/NousResearch/hermes-agent.git
+git clone https://github.com/NousResearch/hermes-agent.git
 cd hermes-agent
+git submodule update --init mini-swe-agent   # required terminal backend
 curl -LsSf https://astral.sh/uv/install.sh | sh
 uv venv .venv --python 3.11
 source .venv/bin/activate
@@ -134,6 +135,12 @@ uv pip install -e "./mini-swe-agent"
 python -m pytest tests/ -q
 ```
 
+> **RL Training (optional):** To work on the RL/Tinker-Atropos integration, also run:
+> ```bash
+> git submodule update --init tinker-atropos
+> uv pip install -e "./tinker-atropos"
+> ```
+
 ---
 
 ## Community