Make chat and embed interfaces provider-agnostic using pydantic_ai

AGENTS.md

@@ -93,3 +93,6 @@ please follow these guidelines:
 
 * **Code Validation**: Don't use `py_compile` for syntax checking.
   Use `pyright` or `make check` instead for proper type checking and validation.
+
+* **Deprecations**: Don't deprecate things -- just delete them and fix the usage sites.
+  Don't create backward compatibility APIs or exports or whatever. Fix the usage sites.

pyproject.toml

@@ -36,6 +36,7 @@ dependencies = [
   "numpy>=2.2.6",
   "openai>=1.81.0",
   "pydantic>=2.11.4",
+  "pydantic-ai-slim[openai]>=1.39.0",
   "pyreadline3>=3.5.4 ; sys_platform == 'win32'",
   "python-dotenv>=1.1.0",
   "tiktoken>=0.12.0",
@@ -85,11 +86,10 @@ dev = [
   "google-auth-httplib2>=0.2.0",
   "google-auth-oauthlib>=1.2.2",
   "isort>=7.0.0",
-  "logfire>=4.1.0", # So 'make check' passes
+  "logfire>=4.1.0",  # So 'make check' passes
   "msgraph-sdk>=1.54.0",
   "opentelemetry-instrumentation-httpx>=0.57b0",
-  "pydantic-ai-slim[openai]>=1.39.0",
-  "pyright>=1.1.408", # 407 has a regression
+  "pyright>=1.1.408",  # 407 has a regression
   "pytest>=8.3.5",
   "pytest-asyncio>=0.26.0",
   "pytest-mock>=3.14.0",