feat(vk): Vk.* - Vulkan 1.0-1.4 generated from the registry, loaded at run time

ludic-dev vkgen reads vk.xml into runtime/native/vk_api.ludic (constants, every struct's
<Struct>_sizeof and <Struct>_<field> offsets, one extern per command) and vk_thunks.ll.
Every size and offset was compiled against the SDK's C headers; `ludic-dev test` checks the
tracked files against the registry wherever the Vulkan SDK is installed.

vk_win.ll (vulkan-1.dll) and vk_mac.ll (libvulkan.1.dylib, MoltenVK) open the loader at run
time, so a program built with Vk.* starts on a machine without Vulkan. ludicc and ludic
build link both for any program that uses Vk.*. The seeds are regenerated for the new
compiler.

vk_probe reports what a machine's Vulkan can do; vk_compute dispatches a Slang compute
shader and reads the picture back, clean under the validation layer on an RTX 3070 Ti and
on an M4 Pro through MoltenVK.

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

selfhost/backend/emit_call.ludic

@@ -909,6 +909,18 @@ function emit_ns_call(ns: pointer, meth: pointer, e: Node) -> Val {
   # 478 gl3.h entry points bound as externs gl_<snake_name>, plus the Ludic
   # helpers (gl_open / gl_swap / gl_screenshot / gl_program / …). Labels are the
   # declaration's parameter names, so `Gl.clear_color(red: 0.1, …)` works.
+  # Vk.* — Vulkan (runtime/native/vk.ludic + the generated vk_api.ludic): the
+  # registry's commands as externs vk_<snake_name>, and the loader and struct helpers.
+  if (ns == "Vk") and (bare == null) {
+    bare = "vk_" + meth
+    var vdecl = find_fn(bare)
+    if (vdecl == null) { vdecl = find_extern(bare) }
+    if (vdecl != null) {
+      let vnames = param_labels(vdecl)
+      var vi = 0
+      while vi < len(vnames) { push(labels, vnames[vi]);  vi += 1 }
+    }
+  }
   if (ns == "Gl") and (bare == null) {
     bare = "gl_" + meth
     var gdecl = find_fn(bare)

selfhost/frontend/parse.ludic

@@ -251,6 +251,8 @@ function p_postfix() -> Node {
       if e.a.kind == E_ID and e.a.s == "Http" { g_uses_http = true }
       # Gl.* — any Gl method splices the OpenGL runtime (and links the GL backend).
       if e.a.kind == E_ID and e.a.s == "Gl" { g_uses_gl = true }
+      # Vk.* — any Vk method splices the Vulkan runtime (and links its loader)
+      if e.a.kind == E_ID and e.a.s == "Vk" { g_uses_vk = true }
       # Tween.to/chain/delay/value/stop/parallel (#48): the fluent stateful handles
       # live in tween.ludic, advanced by an engine-owned system each Update tick.
       if e.a.kind == E_ID and e.a.s == "Tween" and (e.s == "to" or e.s == "chain" or e.s == "delay" or e.s == "value" or e.s == "stop" or e.s == "parallel") { g_uses_tween_rt = true }
@@ -673,6 +675,7 @@ var g_uses_fx: bool = false       # Fx.sparks/number/clear -> splice fx.ludic; f
 var g_uses_audio: bool = false    # Audio.* (#22) -> splice audio.ludic; a windowed build also links audio.ll + AVFoundation
 var g_uses_http:  bool = false    # Http.* (#6) -> splice http.ludic; links http.ll + Foundation (macOS)
 var g_uses_gl:    bool = false    # Gl.* -> splice gl.ludic (+ generated gl_api.ludic); links gl.ll + gl_thunks.ll + OpenGL
+var g_uses_vk:    bool = false    # Vk.* -> splice vk.ludic (+ generated vk_api.ludic); links vk_thunks.ll + the platform loader
 # issue #64: functions marked @System(Phase) in a prebuilt binary module — the
 # compiler registers each with the host at load (it supplies the fn address,
 # which Ludic source cannot take). Parallel arrays: fn name -> phase name.
@@ -1168,6 +1171,13 @@ function maybe_splice_runtime() -> void {
     do_import("runtime/native/gl.ludic")
     cur_dir = saved
   }
+  # Vk.*: splice the Vulkan surface (vk.ludic + the generated vk_api.ludic). The
+  # loader is opened at run time, so a program that never calls Vk.open needs none.
+  if g_uses_vk {
+    cur_dir = ""
+    do_import("runtime/native/vk.ludic")
+    cur_dir = saved
+  }
   # Anim.play/Motion.to sugar (#48): the writes live in systems.ludic and use the
   # reflection ABI, so splice it and force the world table even when the game does
   # not otherwise trip uses_engine_systems.
@@ -1239,6 +1249,7 @@ function parse_program() -> void {
   g_toggled_layers = new []pointer
   g_uses_regex = false
   g_uses_gl = false
+  g_uses_vk = false
   g_uses_bignum = false
   g_uses_dict = false
   g_uses_numeric = false

selfhost/main.ludic

@@ -294,6 +294,15 @@ entry {
       cmd = `{cmd} {gl} {glt} -framework OpenGL`
     }
   }
+  # Vk.* links the generated thunks and the loader that fills them at run time:
+  # vk_win.ll (vulkan-1.dll) on Windows, vk_mac.ll (libvulkan.1.dylib, MoltenVK) on
+  # macOS. Neither links a Vulkan library, so the program starts without one.
+  if g_uses_vk {
+    let vkt = join_path(home, "runtime/native/vk_thunks.ll")
+    var vkl = join_path(home, "runtime/native/vk_mac.ll")
+    if g_target_win { vkl = join_path(home, "runtime/native/vk_win.ll") }
+    cmd = `{cmd} {vkt} {vkl}`
+  }
   # A shipped Windows game is a GUI-subsystem program: started from Explorer, a
   # console-subsystem one opens a console window behind the game. mainCRTStartup keeps
   # the C runtime's ordinary main() entry rather than WinMain.