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

calculators/builder-adversary-lean/run-03/machine-docs/BACKLOG-lex.md

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+# BACKLOG — phase lex (Adversary section)
+
+## Adversary findings
+
+### F1 (advisory) — malformed float literals raise ValueError not LexError
+- `tokenize('.')` raises `ValueError` not `LexError`
+- `tokenize('1.2.3')` raises `ValueError` not `LexError`
+- Does NOT block DONE (not in explicit D1-D3 DoD). Advisory fix: wrap `float()` call in try/except LexError.
+- Opened: 2026-06-15T05:08:00Z | Status: OPEN (advisory)
+
+## Build backlog
+_Read-only to Adversary — Builder manages this section._
+
+- [x] Create calc/lexer.py with Token, LexError, tokenize
+- [x] Create calc/test_lexer.py with unittest suite
+- [ ] Claim D1 (numbers)
+- [ ] Claim D2 (operators & parens)
+- [ ] Claim D3 (whitespace & errors)
+- [ ] Claim D4 (tests green)