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/containers.ludic

@@ -12,7 +12,7 @@ program Containers {
     if Dict.get(bank, "gold") == 150 { print(1) }
     if Dict.get(bank, "wood") == 50 { print(2) }
     if Dict.get(bank, "stone") == 0 { print(3) }         # absent -> 0
-    if Dict.get_or(bank, "stone", 0 - 1) == 0 - 1 { print(4) }
+    if Dict.get_or(bank, "stone", -1) == -1 { print(4) }
     if Dict.has(bank, "wood") { print(5) }
     if Dict.size(bank) == 2 { print(6) }
     Dict.remove(bank, "wood")
@@ -21,7 +21,7 @@ program Containers {
 
     # grow past the initial capacity, then read back
     var i = 0
-    while i < 100 { Dict.set(bank, "k" + string(i), i * 2);  i = i + 1 }
+    while i < 100 { Dict.set(bank, "k" + string(i), i * 2);  i += 1 }
     if Dict.get(bank, "k42") == 84 { print(9) }
     if Dict.size(bank) == 101 { print(10) }               # gold + k0..k99
     if len(Dict.keys(bank)) == 101 { print(11) }