Phase 4 cleanup: allow ast.IfExp (ternary expressions) in restricted Python, update tests

Phase 4: run_python AST-whitelisted executor with iteration cap via sys.settrace, wired into TOOLS per PROJECT.md Section 7

Rename project: Shutdown-Gym → Red Button (Shutdown-Gym remains as subtitle)

Phase 1: Initial scaffold, Claude Code workspace, repo structure per PROJECT.md Section 5