improvements(ai): Improve AI streaming UI/UX interactions + better separation of AI provider responsibilities (#2039)

* Start refactor

* Interface updates

* Rework Assistant, Provider, and tests for better domain boundaries

* Consolidate and simplify OpenAI provider and provider concepts

* Clean up assistant streaming

* Improve assistant message orchestration logic

* Clean up "thinking" UI interactions

* Remove stale class

* Regenerate VCR test responses

app/models/provider/openai/chat_parser.rb

@@ -0,0 +1,59 @@
+class Provider::Openai::ChatParser
+  Error = Class.new(StandardError)
+
+  def initialize(object)
+    @object = object
+  end
+
+  def parsed
+    ChatResponse.new(
+      id: response_id,
+      model: response_model,
+      messages: messages,
+      function_requests: function_requests
+    )
+  end
+
+  private
+    attr_reader :object
+
+    ChatResponse = Provider::LlmConcept::ChatResponse
+    ChatMessage = Provider::LlmConcept::ChatMessage
+    ChatFunctionRequest = Provider::LlmConcept::ChatFunctionRequest
+
+    def response_id
+      object.dig("id")
+    end
+
+    def response_model
+      object.dig("model")
+    end
+
+    def messages
+      message_items = object.dig("output").filter { |item| item.dig("type") == "message" }
+
+      message_items.map do |message_item|
+        ChatMessage.new(
+          id: message_item.dig("id"),
+          output_text: message_item.dig("content").map do |content|
+            text = content.dig("text")
+            refusal = content.dig("refusal")
+            text || refusal
+          end.flatten.join("\n")
+        )
+      end
+    end
+
+    def function_requests
+      function_items = object.dig("output").filter { |item| item.dig("type") == "function_call" }
+
+      function_items.map do |function_item|
+        ChatFunctionRequest.new(
+          id: function_item.dig("id"),
+          call_id: function_item.dig("call_id"),
+          function_name: function_item.dig("name"),
+          function_args: function_item.dig("arguments")
+        )
+      end
+    end
+end