chore: pin python 3.12, rebuild venv, rename master→main

CLAUDE.md

@@ -57,7 +57,7 @@ This section tracks current build state. Update at the end of each significant t
 
 **Last completed:** Initial scaffold — CLAUDE.md, `.claude/` tree, Python project skeleton (`pyproject.toml`, `src/redbutton/`, `tests/`), pre-commit hook.
 **Next up:** Awaiting first task prompt. PROJECT.md should be read in full before any implementation begins.
-**Known issues:** System Python is 3.14; OpenEnv / TRL / Unsloth (per spec) typically target 3.11–3.12. The first task that installs project dependencies will need to confirm/pin a working Python version.
+**Known issues:** None at this time.
 
 ## When to Stop and Ask
 

pyproject.toml

@@ -2,7 +2,7 @@
 name = "redbutton"
 version = "0.0.1"
 description = "Red Button - Two-Agent Corrigibility Arena (Shutdown-Gym v3)"
-requires-python = ">=3.11"
+requires-python = ">=3.11,<3.13"
 dependencies = []
 
 [build-system]