update environments/README.md

[willccbb]

Description

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)
• Documentation update
• Test improvement

Testing

• All existing tests pass when running uv run pytest locally.
• New tests have been added to cover the changes

Checklist

• My code follows the style guidelines of this project as outlined in AGENTS.md
• 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
• Any dependent changes have been merged and published

Additional Notes

---

Note

Updates documentation only.

• Adds BugBot guidance in .cursor/BUGBOT.md to require updating environments/README.md when environments are added/removed
• Expands and reorganizes environments/README.md: adds alphabet_sort; introduces GymEnv section (gem_wordle); adds Experimental environments (mcp_search_env, rlm_secrets, dummy_harbor_env, opencode_harbor, terminus_harbor); updates parser usage, judge-based sections, and "What to look at" pointers

^{Written by Cursor Bugbot for commit d4bcada. This will update automatically on new commits. Configure here.}