feat(gl): OpenGL 4.1 and the ludic.render3d renderer

`Gl.*` binds the whole OpenGL 4.1 core API — every entry point of the
platform gl3.h with every GL_* constant, generated by `ludic-dev glgen`
with per-call ABI thunks. Windowed builds get an NSOpenGLContext on the
existing window at Retina resolution; headless builds render into an
offscreen CGL context, so a program that uses Gl.* renders and
screenshots identically under the test harness. It links gl.ll, the
thunks and OpenGL.framework only when used; every other build stays
byte-identical.

packages/ludic.render3d is a physically based renderer written on that
surface: HDRI image-based lighting, GPU-generated terrain with scanned
PBR materials, CDLOD, cascaded shadows, glTF with skinning, instanced
vegetation with impostors, procedural grass, water, SSAO, and an HDR
pipeline with bloom, auto-exposure and ACES.

It also carries this session's work on it: the terrain at half its cost
(10.3 -> 5.4 ms of frame), the streaming hitch that got worse the longer
you played, a resize that emptied the world, and the packaging that lets
a game use the renderer from its own repository — `ludic assets`, the
material manifest shipping with the package, and shader lookup falling
back to the install root. See changes/ for each, with its numbers.

The camping game that drove all of it has moved out to its own
repository, Maroon Lake; examples/rendering/smooth.ludic stays as the
renderer's example here.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

runtime/native/value.ludic

@@ -221,12 +221,40 @@ function jp_number(p: JP) -> Val {
       di -= 1
     }
     var raw = ip * 65536 + frac
+    raw = jp_exponent(p, raw)
+    if neg != 0 { raw = -raw }
+    return value_fixed(raw)
+  }
+  if p.i < p.n and (p.s[p.i] == 'e' or p.s[p.i] == 'E') {   # 1e-05: an exponent makes it a fixed
+    var raw = jp_exponent(p, ip * 65536)
     if neg != 0 { raw = -raw }
     return value_fixed(raw)
   }
   if neg != 0 { ip = -ip }
   return value_int(ip)
 }
+# an optional exponent after a number's digits, applied to a raw Q16.16 value. Exporters
+# write noise like 7.49e-09 for a zero; a fixed rounds that to 0, which is what it was.
+function jp_exponent(p: JP, raw0: int) -> int {
+  var raw = raw0
+  if p.i >= p.n or (p.s[p.i] != 'e' and p.s[p.i] != 'E') { return raw }
+  p.i += 1
+  var eneg = 0
+  if p.i < p.n and p.s[p.i] == '-' { eneg = 1;  p.i += 1 }
+  else if p.i < p.n and p.s[p.i] == '+' { p.i += 1 }
+  var e = 0
+  while p.i < p.n and p.s[p.i] >= '0' and p.s[p.i] <= '9' {
+    e = e * 10 + (p.s[p.i] - 48)
+    p.i += 1
+  }
+  if e > 12 { e = 12 }
+  var k = 0
+  while k < e {
+    if eneg != 0 { raw = raw / 10 } else { raw = raw * 10 }
+    k += 1
+  }
+  return raw
+}
 
 function jp_list(p: JP) -> Val {
   let out = value_list()