Claude/define milestones mh hj j (#11)

* Add executable milestones roadmap

Define 16 milestones from foundation (complete) through 1.0 release,
with specific verification commands for each task. Includes dependency
graph and immediate next actions prioritized for unblocking progress.

* Implement binary and unary operators throughout compiler

- Add BinOp enum (Add, Sub, Mul, Div, Mod, Lt, Le, Gt, Ge, Eq, Ne, And, Or)
- Add UnaryOp enum (Not, Neg)
- Add ExprKind::BinOp and ExprKind::UnaryOp AST variants
- Fix parser to generate proper operator AST nodes (were returning dummies)
- Add operator evaluation handlers to interpreter
- Add all crates to workspace with proper dependencies

Completes M2 milestone: Parser now handles all operators correctly.

* Update MILESTONES.md with parser progress

Mark parser tasks as complete:
- Let bindings, functions, application
- Products, sums, regions, borrows, conditionals
- Binary operators with proper AST nodes
- Unary operators (!, -)
- Operator precedence hierarchy

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Co-authored-by: Claude <noreply@anthropic.com>

Author: hyperpolymath