Fix captured_vars lookup for SlotNumber(1) in optimize=false IR

Closure field access getfield(#self#, :name) uses Core.Argument(1) in
optimized IR but Core.SlotNumber(1) in unoptimized IR. Handle both.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Dale-Black

src/compiler/codegen.jl

@@ -827,7 +827,9 @@ function compile_call(ctx::JSCompilationContext, expr::Expr)
         obj = args[2]
         field_arg = args[3]
         # Closure captured variable: getfield(self, :name)
-        if obj isa Core.Argument && obj.n == 1 && field_arg isa QuoteNode && field_arg.value isa Symbol
+        # In optimized IR: Core.Argument(1), in unoptimized IR: Core.SlotNumber(1)
+        is_self = (obj isa Core.Argument && obj.n == 1) || (obj isa Core.SlotNumber && obj.id == 1)
+        if is_self && field_arg isa QuoteNode && field_arg.value isa Symbol
             fname = field_arg.value
             if haskey(ctx.captured_vars, fname)
                 return ctx.captured_vars[fname]