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/tiled_p4.ludic

@@ -51,11 +51,11 @@ program TiledP4 {
 
     # --- the design's named fixture: orthogonal-outside.tmx object shapes ---
     let og = Tiled.load("assets/tiled-fixtures/orthogonal-outside.tmx")
-    var olayer = 0 - 1
+    var olayer = -1
     var oli = 0
     while oli < Tiled.layer_count(og) {
       if Tiled.object_count(og, oli) > 0 { olayer = oli }
-      oli = oli + 1
+      oli += 1
     }
     var nell = 0
     var npt = 0
@@ -64,11 +64,11 @@ program TiledP4 {
     var oi = 0
     while oi < Tiled.object_count(og, olayer) {
       let sh = Tiled.object_shape(Tiled.object(og, olayer, oi))
-      if sh == "ellipse" { nell = nell + 1 }
-      if sh == "point" { npt = npt + 1 }
-      if sh == "polygon" { npg = npg + 1 }
-      if sh == "polyline" { npl = npl + 1 }
-      oi = oi + 1
+      if sh == "ellipse" { nell += 1 }
+      if sh == "point" { npt += 1 }
+      if sh == "polygon" { npg += 1 }
+      if sh == "polyline" { npl += 1 }
+      oi += 1
     }
     if nell == 1 and npt == 1 and npg == 1 { print(17) }
     if npl == 2 { print(18) }