feat(input): #89 cursor capture — Input.cursor_mode (hide/lock/confine)

A windowed action game can hide the OS cursor and lock/confine the mouse to the
window. Input.cursor_mode(mode): 0 normal, 1 hidden (draw your own reticle),
2 locked (hidden + dissociated — the mouse feeds relative motion via
Input.mouse_dx/dy and Input.mouse_x/y is a clamped virtual cursor, FPS/twin-stick
aim), 3 confined (dissociated but visible; the mouse can't leave the window).
The platform auto-releases (shows + reconnects) while the window is not key
(Cmd-Tab) and on close, so the cursor is never left captured. Headless it is a
no-op (DCE'd).

Native macOS impl in cocoa.ll: [NSCursor hide]/[unhide] (ref-counted, toggled
only on change so the count stays balanced across focus changes),
CGAssociateMouseAndMouseCursorPosition, and CGGetLastMouseDelta for the relative
virtual cursor, behind a new win_cursor_mode intrinsic. Windowed-only behaviour
(not in the headless golden suite); example compiles headless and links
windowed. Full suite 115/0, fixpoint holds.

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

selfhost/backend/emit_call.ludic

@@ -263,6 +263,7 @@ function emit_ns_call(ns: pointer, meth: pointer, e: Node) -> Val {
     if (meth == "touch_x")      { bare = "input_touch_x";      push(labels, "index") }
     if (meth == "touch_y")      { bare = "input_touch_y";      push(labels, "index") }
     if (meth == "set_touch")    { bare = "input_set_touch";    push(labels, "index"); push(labels, "x"); push(labels, "y"); push(labels, "active") }
+    if (meth == "cursor_mode")  { bare = "input_cursor_mode";  push(labels, "mode") }   # #89 cursor capture
   }
   # Audio.* (#22) — sfx/music playback over the platform audio backend
   # (runtime/native/audio.ludic + audio.ll). Playback is out-of-band; the

selfhost/backend/emit_head.ludic

@@ -68,6 +68,7 @@ function emit_header() -> void {
   emith("declare void @win_mouse(ptr)\n")
   emith("declare void @win_pad(ptr)\n")
   emith("declare void @win_touch(ptr)\n")
+  emith("declare void @win_cursor_mode(i32)\n")
   emith("declare ptr @snd_load(ptr)\n")               # #22 audio backend (audio.ll)
   emith("declare void @snd_play(ptr, i32, i32, i32)\n")
   emith("declare void @snd_stop(ptr)\n")

selfhost/backend/emit_intrin2.ludic

@@ -13,6 +13,7 @@ function is_intrinsic2(name: pointer) -> bool {
   if (name == "win_running") or (name == "win_close") { return true }
   if (name == "win_held") or (name == "win_mouse") { return true }   # #50 device layer
   if (name == "win_pad") or (name == "win_touch") { return true }    # #51 gamepad / touch
+  if (name == "win_cursor_mode") { return true }                     # #89 cursor capture
   if (name == "snd_load") or (name == "snd_play") or (name == "snd_stop") { return true }   # #22 audio
   if (name == "snd_playing") or (name == "snd_set_volume") or (name == "snd_set_rate") { return true }
   if (name == "hs_req_new") or (name == "hs_req_header") or (name == "hs_req_body") { return true }   # #6 HTTP
@@ -65,6 +66,8 @@ function emit_intrinsic2(name: pointer, e: Node) -> Val {
   # words/point [active, x, y]. Both windowed-only, DCE'd headless.
   if (name == "win_pad")   { let a = arg_code(e, 0);  emit("  call void @win_pad(ptr ");  emit(a);  emit(")\n");  return val("0", "void") }
   if (name == "win_touch") { let a = arg_code(e, 0);  emit("  call void @win_touch(ptr ");  emit(a);  emit(")\n");  return val("0", "void") }
+  # #89 — set the OS cursor capture mode (windowed only; DCE'd headless).
+  if (name == "win_cursor_mode") { let a = arg_code(e, 0);  emit("  call void @win_cursor_mode(i32 ");  emit(a);  emit(")\n");  return val("0", "void") }
   # #22 audio backend — AVAudioPlayer via audio.ll; windowed-only, DCE'd headless.
   if (name == "snd_load") { let a = arg_code(e, 0);  return val(emit_bind(`call ptr @snd_load(ptr {a})`), "pointer") }
   if (name == "snd_play") {

selfhost/frontend/parse.ludic

@@ -196,7 +196,7 @@ function p_postfix() -> Node {
       if e.a.kind == E_ID and e.a.s == "Input" and (e.s == "bind" or e.s == "rebind" or e.s == "poll" or e.s == "down" or e.s == "pressed" or e.s == "record" or e.s == "replay" or e.s == "action" or e.s == "bind_pad" or e.s == "active" or e.s == "just_pressed" or e.s == "just_released") { g_uses_input = true }
       # #50 device layer — any of the multi-key / analog / mouse / gamepad / touch
       # methods also splices input.ludic (Input.key stays bare, no runtime).
-      if e.a.kind == E_ID and e.a.s == "Input" and (e.s == "key_down" or e.s == "key_pressed" or e.s == "key_released" or e.s == "press" or e.s == "release" or e.s == "axis" or e.s == "axis_i" or e.s == "vector" or e.s == "strength" or e.s == "mouse_x" or e.s == "mouse_y" or e.s == "mouse_dx" or e.s == "mouse_dy" or e.s == "mouse_down" or e.s == "wheel" or e.s == "set_mouse" or e.s == "pad_connected" or e.s == "pad_button" or e.s == "pad_axis" or e.s == "set_pad" or e.s == "touch_count" or e.s == "touch_x" or e.s == "touch_y" or e.s == "set_touch") { g_uses_input = true }
+      if e.a.kind == E_ID and e.a.s == "Input" and (e.s == "key_down" or e.s == "key_pressed" or e.s == "key_released" or e.s == "press" or e.s == "release" or e.s == "axis" or e.s == "axis_i" or e.s == "vector" or e.s == "strength" or e.s == "mouse_x" or e.s == "mouse_y" or e.s == "mouse_dx" or e.s == "mouse_dy" or e.s == "mouse_down" or e.s == "wheel" or e.s == "set_mouse" or e.s == "pad_connected" or e.s == "pad_button" or e.s == "pad_axis" or e.s == "set_pad" or e.s == "touch_count" or e.s == "touch_x" or e.s == "touch_y" or e.s == "set_touch" or e.s == "cursor_mode") { g_uses_input = true }
       # Anim.play/clip/on_frame/fired + Motion.to (#48): the ergonomic writes over
       # the SpriteAnim/Motion components live in systems.ludic and use the world
       # table, so splice it and force the reflection ABI even if the game leaves