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/events/program_events.ludic

@@ -11,8 +11,8 @@ program ProgramEvents {
   @Public @OnStart handler Boot { print(1) }        # -> program_start
   @Public @OnQuit  handler Bye  { print(2) }        # -> program_quit
 
-  @On(program_start) handler ModInit { print(100) } # mod boots after the game
-  @On(program_quit)  handler ModDone { print(200) } # mod tears down as the game exits
+  @On(program_start) handler ModInit { print(100) }  # mod boots after the game
+  @On(program_quit)  handler ModDone { print(200) }  # mod tears down as the game exits
 
   handler Run phase Update { quit() }
 }