Add `bind` keyword to tokenizer, parse-bind-feat to parser, and
bind-feat no-op case to compiler. Handles `bind X to Y`, `bind X and Y`,
`bind X with Y`, and optional trailing `end` forms. All 43/44 bind tests
pass (1 is an explicit skip).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>