fix(semantic): stop let-binding scans at arrow functions (#28444)

Stop lexical-declaration ancestry checks at arrow-function boundaries so
a sloppy arrow parameter named `let` is accepted.

Validated with scoped Rust checks, full conformance, parser bindings.

AI-assisted (Codex).

crates/oxc_semantic/src/checker/javascript.rs

@@ -276,7 +276,7 @@ pub fn check_binding_identifier(ident: &BindingIdentifier, ctx: &SemanticBuilder
                         }
                         break;
                     }
-                    AstKind::Function(_) => break,
+                    AstKind::Function(_) | AstKind::ArrowFunctionExpression(_) => break,
                     _ => {}
                 }
             }

tasks/coverage/misc/pass/arrow-let-parameter.cjs

@@ -0,0 +1,4 @@
+const first = let => let;
+let second = (let) => let;
+const third = ({ let }) => let;
+const fourth = (...let) => let;