docs(readme): drop misleading RL install-extras claim, defer to CONTRIBUTING

README.md:163 said atroposlib and tinker were pulled in by .[all,dev], but
.[all] does not include .[rl] — those dependencies live in pyproject.toml's
[rl] extra (lines 95-101). With the original wording, a contributor running
uv pip install -e ".[all,dev]" would not have atroposlib or tinker
installed.

Rather than swap one extra for another (which paths users to either of two
parallel install conventions — pip [rl] extra vs tinker-atropos submodule —
without saying which the project considers canonical), this PR drops the
specific install command from the README and links to CONTRIBUTING.md,
which already documents the actual development setup.

Author: deep-name

README.md

@@ -161,7 +161,7 @@ uv pip install -e ".[all,dev]"
 scripts/run_tests.sh
 ```
 
-> **RL Training (optional):** The RL/Atropos integration (`environments/`) ships via the `atroposlib` and `tinker` dependencies pulled in by `.[all,dev]` — no submodule setup required.
+> **RL Training (optional):** The RL/Atropos integration (`environments/`) — see [`CONTRIBUTING.md`](https://github.com/NousResearch/hermes-agent/blob/main/CONTRIBUTING.md#development-setup) for the full setup.
 
 ---