Add named Marks and cross-room NPC pathfinding

- Mark: a debug non-collidable named destination (pixel-art target icon),
  editor tool + name modal, globally-unique names, programmatic Room:addMark
- NPCs walk to Marks: each RGB copy is a per-room resident (like the player),
  running its own A* on its own colour layer, transferring rooms as it crosses
  seams; rendered and collided by the room it currently stands in
- Player copies are obstacles in NPC pathfinding
- A* is footprint-aware for multi-cell NPCs
- Editor: click an NPC to open a filterable destination picker
- Ink: Dialogue.open binds walk_to; Jorge can be sent to "end"/"begin"
- Fix: a blocked NPC now replans each tick and resumes instead of freezing
- [npc] move diagnostics under DEBUG (start/goal/route or block reason)
- Docs (adding-npcs) + CLAUDE.md LÖVE 11.x/float-colour corrections
- Fix test harness loadSprite stub; movement tests green (28)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

rooms/world.sav

@@ -1,6 +1,7 @@
 {
+width=18,
 height=18,
-lastRoom="blocker_test",
+lastRoom="room_16_17",
 rooms={
 	{
 		name="3",
@@ -281,7 +282,16 @@ rooms={
 		name="white_ok",
 		x=11,
 		y=1
+	},
+	{
+		name="room_16_17",
+		x=16,
+		y=17
+	},
+	{
+		name="testing_movement",
+		x=15,
+		y=17
 	}
-},
-width=18
+}
 }