feat(map-editor): v0.2.0c.1 — drag-paint strokes

LMB-hold strokes a line of paints (Auto-Tile: each hovered vertex;
Direct: each hovered cell as an override). RMB-hold strokes a line
of erases (clear_vertex / clear_override). On mouse-press inside the
UI (toolbar / palette / side-panel) the drag never enters paint-mode
so toolbar interaction stays unaffected.

State machine:
 - press(button) outside UI -> drag_paint = "paint"|"erase"
 - while drag_paint and corresponding button still down -> dispatch
   paint at current snap_vertex / mouse_cell each frame
 - button release -> drag_paint = nil

Idempotency: maps.set_vertex / set_override / clear_* are no-op when
the target state is unchanged, so the per-frame repaint is cheap and
doesn't grow the JSON on save.

manifest.module

@@ -1,6 +1,6 @@
 {
     "id": "map-editor",
-    "version": "0.2.0c",
+    "version": "0.2.0c.1",
     "kind": "module",
     "api": "^0.1",
     "ci_frames": 30,