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/faction.ludic

@@ -55,10 +55,10 @@ function fac_ensure() -> void {
 # Faction.id_of(e) — the faction id an entity carries (-1 if it has no Faction).
 @Namespace(Faction) function faction_id_of(e: int) -> int {
   let P = World.prop_id("Faction")
-  if P < 0 { return 0 - 1 }
-  if World.has(e, P) == 0 { return 0 - 1 }
+  if P < 0 { return -1 }
+  if World.has(e, P) == 0 { return -1 }
   let f = World.field_id(P, "id")
-  if f < 0 { return 0 - 1 }
+  if f < 0 { return -1 }
   return World.get(e, P, f)
 }