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>

examples/library/combat.ludic

@@ -19,7 +19,7 @@ program Combat {
   @export function damage(attack: int, armour: int, roll: int) -> int {
     var raw = attack - armour
     if raw < 1 { raw = 1 }
-    if roll == 20 { raw = raw * CRIT_MULT }
+    if roll == 20 { raw *= CRIT_MULT }
     return raw
   }
 
@@ -29,8 +29,8 @@ program Combat {
     var left = hp
     var n = 0
     while left > 0 {
-      left = left - damage(attack, armour, 0)
-      n = n + 1
+      left -= damage(attack, armour, 0)
+      n += 1
     }
     return n
   }