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_config.rb

@@ -0,0 +1,36 @@
+class Provider::Openai::ChatConfig
+  def initialize(functions: [], function_results: [])
+    @functions = functions
+    @function_results = function_results
+  end
+
+  def tools
+    functions.map do |fn|
+      {
+        type: "function",
+        name: fn[:name],
+        description: fn[:description],
+        parameters: fn[:params_schema],
+        strict: fn[:strict]
+      }
+    end
+  end
+
+  def build_input(prompt)
+    results = function_results.map do |fn_result|
+      {
+        type: "function_call_output",
+        call_id: fn_result[:call_id],
+        output: fn_result[:output].to_json
+      }
+    end
+
+    [
+      { role: "user", content: prompt },
+      *results
+    ]
+  end
+
+  private
+    attr_reader :functions, :function_results
+end