Document quiet make targets with V=1 escape hatch; correct calculator/flip_a_coin output-format docs - Developer-Environment-Setup.md: note that lint/test/security are quiet by default (ok-per-step, full output only on failure) and document the 'make V=1 <target>' escape hatch plus the CI re-trigger caveat. - Plugin-Calculator.md / Plugin-Flip-A-Coin.md: correct default output format and CLI examples to match current JSON-first behavior.
Add documentation for multi-language plugins, security model, and developer setup