feat(control): grid snap, NPC context actions, and overlay dim fix

Re-enable users-branch UI, snap session tokens to square/hex grid from the control preview, refine inactive/open-info NPC menus, block marker actions while an effect brush is active, and dim materials/NPC overlays only when they are open.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/shared/features/usersBranchFeatures.ts

@@ -3,4 +3,4 @@
  * (Players library, run-with-players, circular NPC/player session tokens, disposition UI).
  * Re-enable after QA.
  */
-export const USERS_BRANCH_FEATURES_ENABLED = false;
+export const USERS_BRANCH_FEATURES_ENABLED = true;