fix(compiler): preserve declared type of const references

A const reference lowered to `val(itoa(g.a.ival), "int")` in emit_call.ludic —
the initializer's raw integer bits, hardcoded as `int`. For a fixed const like
`const X: fixed = 10.0` that yielded the Q16.16 bits (655360) typed as int, so
every fixed comparison/arithmetic against it silently broke (it caused an
infinite loop in runtime/native/numeric.ludic, previously worked around with
inline literals).

Fix: a const reference now emits its initializer expression via emit_expr(g.a),
which carries the initializer's real type (E_FLOAT->fixed, E_BOOL->bool,
E_STR->string) and even handles computed initializers. Every existing const is
an int literal, for which this is byte-identical to the old immediate — the
C-free bootstrap fixpoint and all golden renders are unchanged.

- selfhost/tests/const.ludic + sh_case pin fixed/int/bool const behaviour.
- runtime/native/numeric.ludic restored to named fixed consts (HUGE_TEN etc.),
  which the workaround had inlined; the numeric example (20 assertions) still
  passes, validating the fix under runtime splice.

All suites green: x selfhost-test 31/31 (fixpoint holds, goldens byte-identical),
x test 85/85, x test-tools 30/30.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

selfhost/backend/emit_call.ludic

@@ -925,7 +925,11 @@ function emit_expr(e: Node) -> Val {
     if li >= 0 { return emit_load_at(loc_reg[li], loc_ty[li]) }
     let g = find_global(e.s)
     if (g != null) {
-      if g.kind == N_CONST { return val(itoa(g.a.ival), "int") }
+      # a const reference IS its initializer expression, carrying that
+      # expression's real type — so `const X: fixed = 10.0` yields a `fixed`, not
+      # the raw Q16.16 bits mislabelled `int`. Every existing const is an int
+      # literal, for which this is byte-identical to the old immediate.
+      if g.kind == N_CONST { return emit_expr(g.a) }
       let r = emit_bind(`load {llty(g.ty)}, ptr @g_{e.s}`)
       return val(r, g.ty)
     }