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>

packages/ludic.gameplay/combat.ludic

@@ -21,6 +21,9 @@ event cancellable DamageAboutToApply { target: int = 0, src: int = 0, amount: in
 event Damaged { target: int = 0, src: int = 0, amount: int = 0 }
 event Died { e: int = 0, src: int = 0 }
 event Healed { e: int = 0, amount: int = 0 }
+event Crit { target: int = 0, src: int = 0 }     # the attacker's crit_pct fired
+
+var combat_reflecting: bool = false              # thorns never reflect thorns
 
 # the mutable channel for lever 6: listeners rewrite the pending damage here.
 var combat_pending: int = 0
@@ -47,7 +50,11 @@ var combat_pending: int = 0
   let fhp = World.field_id(P, "hp")
   if fhp < 0 { return 0 }
 
-  combat_pending = combat_mitigate(target, amount)
+  # the attacker's build: damage_pct, then a crit_pct chance to double
+  var raw = amount * stats_field(src, "damage_pct", 100) / 100
+  let crit = stats_field(src, "crit_pct", 0)
+  if (crit > 0) and Random.chance(percent: crit) { raw = raw * 2;  emit Crit(target: target, src: src) }
+  combat_pending = combat_mitigate(target, raw)
   if emit DamageAboutToApply(target: target, src: src, amount: combat_pending) != 0 { return 0 }
   var dmg = combat_pending
   if dmg < 0 { dmg = 0 }
@@ -57,6 +64,17 @@ var combat_pending: int = 0
   World.set(target, P, fhp, hp)
   emit Damaged(target: target, src: src, amount: dmg)
   if hp <= 0 { emit Died(e: target, src: src) }
+  # the attacker's leech, and the defender's thorns (never reflected back again)
+  if dmg > 0 {
+    let leech = stats_field(src, "leech_pct", 0)
+    if (leech > 0) and Random.chance(percent: leech) { combat_heal(src, stats_field(src, "leech_hp", 1)) }
+    let thorns = stats_field(target, "thorns", 0)
+    if (thorns > 0) and (src != target) and (not combat_reflecting) and (World.has(src, P) != 0) {
+      combat_reflecting = true
+      combat_damage(src, target, thorns)
+      combat_reflecting = false
+    }
+  }
   return dmg
 }