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

calculators/builder-adversary-stateless/run-04/machine-docs/BACKLOG-eval.md

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+# BACKLOG — phase eval
+
+## Build backlog
+
+- [x] D1 — arithmetic: implement evaluate() for +, -, *, /, precedence, parens, unary minus
+- [x] D2 — division: true division, EvalError on div-by-zero
+- [x] D3 — result type: fmt() strips .0 from whole floats
+- [x] D4 — CLI: calc.py catches errors, stderr, non-zero exit
+- [x] D5 — tests: 11 evaluator tests + full suite green (50 total)
+
+## Adversary findings
+
+(awaiting review)