feat!: migrate to OpenAI native tool calls and fix circular deps (#fuck-gemini)

- Fix circular dependencies in agent/tools
- Migrate from custom JSON to OpenAI tool calls format
- Add async streaming (step_stream, complete_stream)
- Simplify prompt system and remove token counting
- Add 5 new API endpoints (/health, /v1/models, /api/memory/*)
- Add 3 new tools (get_torrent_by_index, add_torrent_by_index, set_language)
- Fix all 500 tests and add coverage config (80% threshold)
- Add comprehensive docs (README, pytest guide)

BREAKING: LLM interface changed, memory injection via get_memory()

agent/llm/__init__.py

@@ -1,5 +1,13 @@
-"""LLM client module."""
+"""LLM clients module."""
+
 from .deepseek import DeepSeekClient
+from .exceptions import LLMAPIError, LLMConfigurationError, LLMError
 from .ollama import OllamaClient
 
-__all__ = ['DeepSeekClient', 'OllamaClient']
+__all__ = [
+    "DeepSeekClient",
+    "OllamaClient",
+    "LLMError",
+    "LLMAPIError",
+    "LLMConfigurationError",
+]