Refactor content generation API and purge legacy documentation

This commit implements a major refactoring of the core generation logic
by removing the Gemini.Generate module and migrating its functionality
into the Gemini.APIs.Coordinator namespace. This change unifies the
interface for content generation and streaming across the library.

Primary modifications:
- Deleted the legacy lib/gemini/apis/generate.ex file.
- Transitioned examples to use the Coordinator for generate_content calls.
- Updated tool calling demos to use internal parsing helpers within the
  Coordinator module.
- Removed the oldDocs directory containing obsolete design specifications,
  telemetry requirements, and refactoring plans.
- Simplified generate_parsing_test.exs by moving general response parsing
  tests to the Coordinator and retaining only tool result helpers.

These changes reduce technical debt by eliminating redundant documentation
and consolidating the service orchestration layer.

Author: nshkrdotcom

examples/demo_unified.exs

@@ -159,16 +159,16 @@ defmodule UnifiedArchitectureDemo do
   end
 
   defp demo_backward_compatibility do
-    IO.puts("\n🔄 Backward Compatibility Demo")
+    IO.puts("\n🔄 API Compatibility Demo")
     IO.puts("-" |> String.duplicate(30))
 
     # Show that existing APIs still work
-    IO.puts("Testing existing API functions...")
+    IO.puts("Testing API functions...")
 
     # These would normally make real API calls, but we'll show they compile and run
     try do
       # This will fail with auth errors, but shows the API is compatible
-      case Gemini.Generate.content("Hello, world!") do
+      case Gemini.APIs.Coordinator.generate_content("Hello, world!") do
         {:ok, _response} ->
           IO.puts("✅ generate_content API compatible")
 
@@ -180,15 +180,6 @@ defmodule UnifiedArchitectureDemo do
         IO.puts("✅ generate_content API compatible (compilation successful)")
     end
 
-    # Show that build_generate_request is now public
-    try do
-      request = Gemini.Generate.build_generate_request("Test", [])
-      IO.puts("✅ build_generate_request is public: #{map_size(request)} fields")
-    rescue
-      error ->
-        IO.puts("❌ build_generate_request error: #{inspect(error)}")
-    end
-
     # Test configuration functions
     model = Gemini.Config.default_model()
     IO.puts("✅ Default model: #{model}")

examples/tool_calling_demo.exs

@@ -3,7 +3,7 @@
 # Tool Calling Demo
 # This example demonstrates the deserialization and serialization of tool calling data
 
-alias Gemini.Generate
+alias Gemini.APIs.Coordinator
 alias Gemini.Types.Content
 alias Altar.ADM.ToolResult
 
@@ -33,7 +33,7 @@ mock_api_response = %{
   ]
 }
 
-case Generate.parse_generate_response(mock_api_response) do
+case Coordinator.__test_parse_generate_response__(mock_api_response) do
   {:ok, response} ->
     IO.puts("✅ Successfully parsed response!")
 
@@ -107,7 +107,7 @@ malformed_response = %{
   ]
 }
 
-case Generate.parse_generate_response(malformed_response) do
+case Coordinator.__test_parse_generate_response__(malformed_response) do
   {:ok, _response} ->
     IO.puts("❌ Should have failed!")