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

calculators/builder-adversary-stateless/run-02/machine-docs/DECISIONS.md

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+# DECISIONS (append-only, settled design decisions)
+
+## lex phase
+
+**D-LEX-1:** `Token` uses `@dataclass` for equality and repr, making test assertions clean.
+
+**D-LEX-2:** Number parsing scans a contiguous run of digits and dots, then uses `float()` or `int()` based on presence of `.`. Edge cases `.5` and `10.` handled correctly by Python's built-in conversion.
+
+**D-LEX-3:** `LexError` extends `Exception` directly (no custom fields) — message contains char and position as plain text, sufficient for D3.
+
+**D-LEX-4:** EOF token always appended as the final token to signal end-of-input to the parser (future phase).
+
+## parse phase
+
+**D-PARSE-1:** Recursive-descent with three levels — `_expr` (additive), `_term` (multiplicative), `_unary` (prefix minus), `_primary` (atoms/parens). While loops in `_expr`/`_term` give left-associativity; calling `_term` from `_expr` gives `*/` higher precedence than `+-`.
+
+**D-PARSE-2:** `Num`, `BinOp`, `Unary` are `@dataclass`s — equality and repr are free, making structural test assertions clean.
+
+**D-PARSE-3:** `ParseError` extends `Exception` directly. Message contains the unexpected token kind/value, sufficient for D5.