Language strictness config

Checks that Rust, Python, Go and shell projects configure their compilers, linters and type checkers strictly: Cargo [lints], unsafe_code and overflow-checks; a Python type checker (mypy strict, pyright mode) and linter; golangci-lint config and //nolint density; and `set -euo pipefail` in shell scripts. Reads configuration files only; nothing is executed. These are hygiene checks, so severities are info/low and the shell check is low-confidence. TypeScript strictness is covered elsewhere.