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.gameplay/combat.ludic

@@ -53,7 +53,7 @@ var combat_pending: int = 0
   # 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) }
+  if (crit > 0) and Random.chance(percent: crit) { 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