Wire view-mode toggles (alt-view + coordinate grid) via new ViewModeController

Moves the AlternateViewEvent / ToggleCoordinateGridEvent subscriptions out of
ClientGameRunner into a dedicated controller in src/client/controllers/. Also
wires ToggleCoordinateGridEvent (M keybind) — previously emitted with no
listener — so the persistent coordinate-grid toggle works. Grid + alt-view
hide names only under alt-view; M keeps names visible.

src/client/render/gl/render-settings.json

@@ -255,7 +255,7 @@
     "gradientSolidEnd": 0.1
   },
   "altView": {
-    "gridFontSize": 16,
+    "gridFontSize": 24,
     "recolorStructures": true
   },
   "tileDrip": {