feat(api): add shop action support with next_round functionality

- Add shop function to handle shop state actions
- Implement next_round action to transition from shop to blind select
- Add ShopActionArgs type definition with action field
- Include validation for shop state before action execution
- Add pending request handling for state transitions

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

Author: S1M0N38

src/lua/api.lua

@@ -334,6 +334,35 @@ API.functions["cash_out"] = function(_)
   }
 end
 
+---Selects an action for shop
+---@param args ShopActionArgs The shop action to perform
+API.functions["shop"] = function(args)
+  -- Validate current game state is appropriate for shop
+  if G.STATE ~= G.STATES.SHOP then
+    API.send_error_response("Cannot select shop action when not in shop", { current_state = G.STATE })
+    return
+  end
+
+  local action = args.action
+  if action == "next_round" then
+    G.FUNCS.toggle_shop({})
+    API.pending_requests["shop"] = {
+      condition = function()
+        return G.STATE == G.STATES.BLIND_SELECT
+          and #G.E_MANAGER.queues.base < EVENT_QUEUE_THRESHOLD
+          and G.STATE_COMPLETE
+      end,
+      action = function()
+        local game_state = utils.get_game_state()
+        API.send_response(game_state)
+      end,
+    }
+  else
+    API.send_error_response("Invalid action arg for shop", { action = action })
+    return
+  end
+end
+
 ---Selects an action for booster packs (TODO implement)
 ---@param _ table Arguments
 API.functions["select_booster_action"] = function(_)

src/lua/types.lua

@@ -46,6 +46,12 @@
 ---@field action "play_hand" | "discard" The action to perform
 ---@field cards number[] Array of card indices (0-based)
 
+---@class ShopActionArgs
+---@field action "next_round" The action to perform
+
+-- TODO: add the other actions "reroll" | "buy" | "buy_and_use" | "redeem" | "open"
+--@field item number? The item to buy/buy_and_use/redeem/open (0-based)
+
 -- =============================================================================
 -- Main API Module (defined in api.lua)
 -- =============================================================================