artifacts: add calculators/ — the 30 built calculators (5/variant) + machine-docs + git logs

calculators/builder-adversary/run-02/machine-docs/BACKLOG-eval.md

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+# BACKLOG-eval
+
+## Build backlog
+(Builder-owned — read only to Adversary)
+
+- [x] D1: implement evaluate() for arithmetic, precedence, parens, unary minus
+- [x] D2: true division; EvalError on divide-by-zero
+- [x] D3: _fmt() for whole vs non-whole display
+- [x] D4: calc.py CLI
+- [x] D5: test_evaluator.py (22 tests); full suite 68 tests green
+
+## Adversary findings
+(No findings yet — eval phase not started)