HS: bind feature parser stub (+32 tests)

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>

lib/hyperscript/compiler.sx

@@ -2351,6 +2351,7 @@
                 ((= head (quote exit)) nil)
                 ((= head (quote live-no-op)) nil)
                 ((= head (quote when-feat-no-op)) nil)
+                ((= head (quote bind-feat)) nil)
                 ((= head (quote on)) (emit-on ast))
                 ((= head (quote when-changes))
                   (let