refactor(runtime,packages,examples): named constants, package enums, idiom sweep

- runtime: HEADLESS_FRAME_PATH, STICK_DEADZONE / STICK_LEFT_X/Y, key and
  byte codes as char literals throughout (`k == 'w'`, `fill(rt_map, ' ', …)`)
- ludic.gameplay/stats: drop the duplicate `stat_field` (it answered "atk"
  for every build stat); Stats.base uses stats_field_name
- ludic.shooter: compare aim modes and fire patterns with AimMode.* and
  WeaponPattern.* instead of raw ints; STICK_RIGHT_X/Y
- ludic.npcai: DecisionMade / brain_set_state use AiState.*
- examples/games/menu.ludic uses Font.load / Ui.* with FONT_PATH and
  BACKDROP named; strings.ludic header says what it prints
- whole tree: `x = x + 1` → `x += 1` (single-term right-hand sides only),
  `0 - x` → `-x`, ASCII codes → char literals; every .ludic and every
  ```ludic fence reformatted with the fixed formatter (whitespace only)

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

packages/ludic.rpg/status.ludic

@@ -22,7 +22,7 @@ event StatusExpired { target: int = 0, kind: int = 0 }
 # Status.apply(target, kind, amount, interval, ttl) — attach a timed effect.
 @Namespace(Status) function status_apply(target: int, kind: int, amount: int, interval: int, ttl: int) -> int {
   let m = World.model_id("StatusFx")
-  if m < 0 { return 0 - 1 }
+  if m < 0 { return -1 }
   let e = World.spawn(m)
   let P = World.prop_id("Status")
   World.set(e, P, World.field_id(P, "target"), target)