0.0.1

Fix grammar, math rendering, and add physics demo examples

Grammar:
- Support tuple indexing {(i,j) in S} via ParenExpr accepting ExprList
- Fix constraint body parsing (CompareOp conflict with expression grammar)
- Support printf without colon prefix

Math renderer:
- Fix constraint indexing display (use \forall notation)
- Escape underscores in objective names inside \text{}
- Wrap declaration indexing in \{...\} braces

Demo:
- Replace energy domain example with 5 famous physics examples:
  Brachistochrone, Fermat's Principle, Ising Model, Kepler Orbit
  Transfer, Kirchhoff Circuit Network
- Add example picker UI with styled buttons

Tests: 33 passing (4 new grammar tests for tuple indexing and printf)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>