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/games/menu.ludic

@@ -4,6 +4,11 @@
 # and activation. The game only loads a font, opens the UI, and reads clicks.
 program Menu {
 
+  # the macOS system font: the toolchain targets macOS today, and the sample keeps
+  # the repo free of a bundled font
+  const FONT_PATH: string = "/System/Library/Fonts/Supplemental/Arial.ttf"
+  const BACKDROP: int = 0x0e0e16
+
   var title_font: int = 0
 
   ui MainMenu {
@@ -19,22 +24,22 @@ program Menu {
   }
 
   handler Boot phase Start {
-    title_font = font_load("/System/Library/Fonts/Supplemental/Arial.ttf")
-    ui_build()
-    ui_open(UI_MainMenu)
+    title_font = Font.load(FONT_PATH)
+    Ui.build()
+    Ui.open(UI_MainMenu)
   }
 
   handler Nav phase Update {
-    ui_tick(Input.key())
-    if ui_clicked(UI_NewGame)  { ui_set_text(UI_NewGame, "Starting...") }
-    if ui_clicked(UI_Continue) { ui_set_text(UI_Continue, "No save") }
-    if ui_clicked(UI_Options)  { ui_set_text(UI_Options, "Soon (TM)") }
-    if ui_clicked(UI_Quit)     { quit() }
+    Ui.tick(Input.key())
+    if Ui.clicked(UI_NewGame)  { Ui.set_text(UI_NewGame, "Starting...") }
+    if Ui.clicked(UI_Continue) { Ui.set_text(UI_Continue, "No save") }
+    if Ui.clicked(UI_Options)  { Ui.set_text(UI_Options, "Soon (TM)") }
+    if Ui.clicked(UI_Quit)     { quit() }
   }
 
   handler Draw phase Render {
-    Screen.clear(0x0e0e16)
-    ui_render()
+    Screen.clear(BACKDROP)
+    Ui.render()
     Screen.show()
   }
 }