feat(engine): #90 atlas-aware Sprite component, #91 become from listeners, 0.3.x ergonomics batch

Closes the two open issues and lands the pending unreleased batch:

- #90: `Sprite { atlas: 1 }` routes esys_sprite through atlas_draw_ex
  (scale/flip/tint), so cell / cell_span / strip ids of any size draw
  through the engine sprite-render system. examples/library/sprite_atlas
  is the pixel-readback regression.
- #91: `become` from an @On(Event) listener / global handler / plain
  function no longer segfaults the compiler; it emits @L_scene_leave()
  (a dispatch on the live scene id) so the leaving scene's on-exit runs.
  UI_* handles are readable from any code (widget table built on first
  use). examples/library/scene_menus covers it.
- fix: a windowed `ludicc -o` build that reaches the audio runtime only
  through the atlas/Assets preload import now links audio.ll +
  AVFoundation (the audio backend link was gated on a game-level
  Audio.* call, so any windowed game declaring Sprite failed to link).
- the hand-written "Unreleased" CHANGELOG section is converted to
  changesets under changes/ so `x release` generates it.
- plus the batch: engine-driven retained UI + UiClicked event, Overlay
  phase, TileSkin tilemap-render system, Key.* constants, Font/Ui/File
  namespaces, Sprite.strip, prefabs, managers, countdown fields,
  enum-typed machines, layer @Queries, ludic.prefs / ludic.dungeon
  packages, Ai.seek pathing, Solids.solid2, cursor confine (mode 3)
  fix, shooter centre-aim fix, reserved-word function diagnostic.

Verified: x test (124/124), x test-tools, check-impl, check-vocabulary,
check-docs, docs-gen + docs-check, bootstrap-cfree (seed is a fixpoint).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

selfhost/backend/stdlib/emit_key.ludic

@@ -0,0 +1,34 @@
+# emit_key.ludic — `Key.Name` -> the key code the input layer delivers, folded at
+# compile time (like Color.*). Letters are the lowercase character (what the held-key
+# set stores), digits their ASCII, plus the specials. Arrow keys alias WASD because the
+# platform layer maps them that way; Escape is 27 (0.3, #88).
+function key_lookup(name: pointer) -> int {
+  if (name == "Space")     { return 32 }
+  if (name == "Enter")     { return 10 }
+  if (name == "Return")    { return 10 }
+  if (name == "Escape")    { return 27 }
+  if (name == "Esc")       { return 27 }
+  if (name == "Shift")     { return 16 }
+  if (name == "Tab")       { return 9 }
+  if (name == "Backspace") { return 8 }
+  if (name == "Up")        { return 119 }
+  if (name == "Down")      { return 115 }
+  if (name == "Left")      { return 97 }
+  if (name == "Right")     { return 100 }
+  if (name == "Digit0") { return 48 }
+  if (name == "Digit1") { return 49 }
+  if (name == "Digit2") { return 50 }
+  if (name == "Digit3") { return 51 }
+  if (name == "Digit4") { return 52 }
+  if (name == "Digit5") { return 53 }
+  if (name == "Digit6") { return 54 }
+  if (name == "Digit7") { return 55 }
+  if (name == "Digit8") { return 56 }
+  if (name == "Digit9") { return 57 }
+  # a single capital letter names that letter key: Key.A .. Key.Z
+  if (name[1] == 0) {
+    let c = name[0]
+    if (c >= 65) and (c <= 90) { return c + 32 }
+  }
+  return 0 - 1
+}