feat(lang): L4 type checker between parse and emit

selfhost/check/ walks every function, the entry, tests, globals' initializers and
@On listeners with real scopes, and refuses mixed number kinds, text and numbers,
two record types, mismatched slices and fn types, wrong argument counts, wrong
returns and wrong push elements - every mix-up at once, each at its line.
LUDIC_CHECK_REPORT=1 lists them by category. pointer stays untyped (L7's).

What it found is fixed: render3d's HDR scan calling the float-bits extern f_lt
with floats; ludic.shooter's right-stick aim overflowing past half a push;
prof.ludic storing longs in []int; extern arguments now coerced to their
parameters. Text-returning runtime functions say string; Assets.ready says bool.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

selfhost/backend/game/emit_machine.ludic

@@ -30,7 +30,7 @@ function machine_state_value(m: Node, state: Node) -> pointer {
 
 function emit_machine(st: Node) -> void {
   let gv = machine_var(st.a)
-  var s = ""
+  var s: pointer = ""
   if (gv != null) { s = emit_bind(`load i32, ptr @g_{st.a.s}`) }
   else {
     let regv = emit_expr(st.a)