feat(editor): add entity operations for overworld editing

- Introduced new `entity_operations.cc` and `entity_operations.h` files to handle the insertion of entrances, exits, sprites, and items in the overworld editor.
- Updated `map_properties.cc` to include a context menu for entity insertion, allowing users to add various entities directly from the canvas.
- Enhanced `overworld_editor.cc` to manage entity insertion callbacks and streamline the editing process.

Benefits:
- Improves the functionality of the overworld editor by enabling direct manipulation of entities.
- Provides a more intuitive user experience with context-sensitive menus for entity operations.

src/app/editor/overworld/entity_operations.h

@@ -0,0 +1,136 @@
+#ifndef YAZE_APP_EDITOR_OVERWORLD_ENTITY_OPERATIONS_H
+#define YAZE_APP_EDITOR_OVERWORLD_ENTITY_OPERATIONS_H
+
+#include "absl/status/statusor.h"
+#include "zelda3/overworld/overworld.h"
+#include "zelda3/overworld/overworld_entrance.h"
+#include "zelda3/overworld/overworld_exit.h"
+#include "zelda3/overworld/overworld_item.h"
+#include "zelda3/sprite/sprite.h"
+#include "imgui/imgui.h"
+
+namespace yaze {
+namespace editor {
+
+/**
+ * @brief Flat helper functions for entity insertion/manipulation
+ * 
+ * Following ZScream's entity management pattern (EntranceMode.cs, ExitMode.cs, etc.)
+ * but implemented as free functions to minimize state management.
+ * 
+ * Key concepts from ZScream:
+ * - Find first deleted slot for insertion
+ * - Calculate map position from mouse coordinates
+ * - Use parent map ID for multi-area maps
+ * - Call UpdateMapProperties to sync position data
+ */
+
+/**
+ * @brief Insert a new entrance at the specified position
+ * 
+ * Follows ZScream's EntranceMode.AddEntrance() logic (EntranceMode.cs:53-148):
+ * - Finds first deleted entrance slot
+ * - Snaps position to 16x16 grid
+ * - Uses parent map ID for multi-area maps
+ * - Calls UpdateMapProperties to calculate game coordinates
+ * 
+ * @param overworld Overworld data containing entrance arrays
+ * @param mouse_pos Mouse position in canvas coordinates (world space)
+ * @param current_map Current map index being edited
+ * @param is_hole True to insert a hole instead of entrance
+ * @return Pointer to newly inserted entrance, or error if no slots available
+ */
+absl::StatusOr<zelda3::OverworldEntrance*> InsertEntrance(
+    zelda3::Overworld* overworld, ImVec2 mouse_pos, int current_map, 
+    bool is_hole = false);
+
+/**
+ * @brief Insert a new exit at the specified position
+ * 
+ * Follows ZScream's ExitMode.AddExit() logic (ExitMode.cs:59-124):
+ * - Finds first deleted exit slot
+ * - Snaps position to 16x16 grid
+ * - Initializes exit with default scroll/camera values
+ * - Sets room ID to 0 (needs to be configured by user)
+ * 
+ * @param overworld Overworld data containing exit arrays
+ * @param mouse_pos Mouse position in canvas coordinates
+ * @param current_map Current map index being edited
+ * @return Pointer to newly inserted exit, or error if no slots available
+ */
+absl::StatusOr<zelda3::OverworldExit*> InsertExit(
+    zelda3::Overworld* overworld, ImVec2 mouse_pos, int current_map);
+
+/**
+ * @brief Insert a new sprite at the specified position
+ * 
+ * Follows ZScream's SpriteMode sprite insertion (SpriteMode.cs:27-100):
+ * - Adds new sprite to game state array
+ * - Calculates map position and game coordinates
+ * - Sets sprite ID (default 0, user configures in popup)
+ * 
+ * @param overworld Overworld data containing sprite arrays
+ * @param mouse_pos Mouse position in canvas coordinates
+ * @param current_map Current map index being edited
+ * @param game_state Current game state (0=beginning, 1=zelda, 2=agahnim)
+ * @param sprite_id Sprite ID to insert (default 0)
+ * @return Pointer to newly inserted sprite
+ */
+absl::StatusOr<zelda3::Sprite*> InsertSprite(
+    zelda3::Overworld* overworld, ImVec2 mouse_pos, int current_map, 
+    int game_state, uint8_t sprite_id = 0);
+
+/**
+ * @brief Insert a new item at the specified position
+ * 
+ * Follows ZScream's ItemMode item insertion (ItemMode.cs:54-113):
+ * - Adds new item to all_items array
+ * - Calculates map position and game coordinates
+ * - Sets item ID (default 0, user configures in popup)
+ * 
+ * @param overworld Overworld data containing item arrays
+ * @param mouse_pos Mouse position in canvas coordinates
+ * @param current_map Current map index being edited
+ * @param item_id Item ID to insert (default 0x00 - Nothing)
+ * @return Pointer to newly inserted item
+ */
+absl::StatusOr<zelda3::OverworldItem*> InsertItem(
+    zelda3::Overworld* overworld, ImVec2 mouse_pos, int current_map,
+    uint8_t item_id = 0);
+
+/**
+ * @brief Helper to get parent map ID for multi-area maps
+ * 
+ * Returns the parent map ID, handling the case where a map is its own parent.
+ * Matches ZScream logic where ParentID == 255 means use current map.
+ */
+inline uint8_t GetParentMapId(const zelda3::OverworldMap* map, int current_map) {
+  uint8_t parent = map->parent();
+  return (parent == 0xFF) ? static_cast<uint8_t>(current_map) : parent;
+}
+
+/**
+ * @brief Snap position to 16x16 grid (standard entity positioning)
+ */
+inline ImVec2 SnapToEntityGrid(ImVec2 pos) {
+  return ImVec2(
+    static_cast<float>(static_cast<int>(pos.x / 16) * 16),
+    static_cast<float>(static_cast<int>(pos.y / 16) * 16)
+  );
+}
+
+/**
+ * @brief Clamp position to valid overworld bounds
+ */
+inline ImVec2 ClampToOverworldBounds(ImVec2 pos) {
+  return ImVec2(
+    std::clamp(pos.x, 0.0f, 4080.0f),  // 4096 - 16
+    std::clamp(pos.y, 0.0f, 4080.0f)
+  );
+}
+
+}  // namespace editor
+}  // namespace yaze
+
+#endif  // YAZE_APP_EDITOR_OVERWORLD_ENTITY_OPERATIONS_H
+