Refactor Agent Commands and Enhance Resource Context Management

- Updated the immediate action plan to focus on integrating `Tile16ProposalGenerator` and `ResourceContextBuilder` into agent commands, improving command handling and proposal generation.
- Implemented the `SetTile` method in the `Overworld` class to facilitate tile modifications based on the current world context.
- Enhanced error handling in command execution to ensure robust feedback during ROM operations.
- Created new files for `Tile16ProposalGenerator` and `ResourceContextBuilder`, enabling structured management of tile changes and resource labels for AI prompts.

This commit advances the functionality of the z3ed system, laying the groundwork for more sophisticated AI-driven editing capabilities.

src/app/zelda3/overworld/overworld.h

@@ -287,6 +287,15 @@ class Overworld {
       return map_tiles_.special_world[y][x];
     }
   }
+  void SetTile(int x, int y, uint16_t tile_id) {
+    if (current_world_ == 0) {
+      map_tiles_.light_world[y][x] = tile_id;
+    } else if (current_world_ == 1) {
+      map_tiles_.dark_world[y][x] = tile_id;
+    } else {
+      map_tiles_.special_world[y][x] = tile_id;
+    }
+  }
   auto map_tiles() const { return map_tiles_; }
   auto mutable_map_tiles() { return &map_tiles_; }
   auto all_items() const { return all_items_; }