Standardize toolchain across the matrix: Python 3.12 floor (no version-pinned
shebangs; ISO-time symlink python3->python3.N + uv for venvs), Node LTS
(flags debby Node22 vs FreeBSD node24 divergence to resolve), Rust/Go/Zig
and managed tools (tmux/codex/pi/zot) conventions.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>