Add embedding support for Gemini provider

Enables text embedding functionality using Gemini's OpenAI-compatible embeddings endpoint.

Implementation:
- Add embed_request_type class method returning OpenAI::Embedding::RequestType (Gemini uses same request format as OpenAI)
- Add api_embed_execute with connection error handling and instrumentation
- Add Gemini::Embedding::RequestType alias in _types.rb

Test coverage (1 test, 1 assertion):
- embed_request_type returns OpenAI::Embedding::RequestType instance

Author: aoki-ryusei

lib/active_agent/providers/gemini/_types.rb

@@ -2,12 +2,18 @@
 
 require_relative "options"
 require_relative "../open_ai/chat/_types"
+require_relative "../open_ai/embedding/_types"
 
 module ActiveAgent
   module Providers
     module Gemini
       # Reuse OpenAI Chat request type (same API format)
       RequestType = OpenAI::Chat::RequestType
+
+      # Reuse OpenAI Embedding types (same API format)
+      module Embedding
+        RequestType = OpenAI::Embedding::RequestType
+      end
     end
   end
 end

lib/active_agent/providers/gemini_provider.rb

@@ -30,6 +30,11 @@ def self.prompt_request_type
         namespace::RequestType.new
       end
 
+      # @return [ActiveModel::Type::Value]
+      def self.embed_request_type
+        namespace::Embedding::RequestType.new
+      end
+
       protected
 
       # Executes chat completion request with Gemini-specific error handling.
@@ -46,6 +51,18 @@ def api_prompt_execute(parameters)
         raise exception
       end
 
+      # Executes embedding request with Gemini-specific error handling.
+      #
+      # @param parameters [Hash]
+      # @return [Hash] symbolized API response
+      # @raise [OpenAI::Errors::APIConnectionError] when Gemini API unreachable
+      def api_embed_execute(parameters)
+        client.embeddings.create(**parameters).as_json.deep_symbolize_keys
+      rescue ::OpenAI::Errors::APIConnectionError => exception
+        log_connection_error(exception)
+        raise exception
+      end
+
       # Merges streaming delta into the message with role cleanup.
       #
       # Overrides parent to handle Gemini's role copying behavior which duplicates

test/providers/gemini/gemini_provider_test.rb

@@ -38,6 +38,13 @@ class GeminiProviderTest < ActiveSupport::TestCase
     assert_instance_of ActiveAgent::Providers::OpenAI::Chat::RequestType, request_type
   end
 
+  test "embed_request_type returns OpenAI::Embedding::RequestType" do
+    request_type = ActiveAgent::Providers::GeminiProvider.embed_request_type
+
+    # Gemini::Embedding::RequestType is aliased to OpenAI::Embedding::RequestType
+    assert_instance_of ActiveAgent::Providers::OpenAI::Embedding::RequestType, request_type
+  end
+
   test "initializes provider with valid configuration" do
     provider = ActiveAgent::Providers::GeminiProvider.new(@valid_config)