Initial project structure

Scaffold all modules, route stubs, data models, and config.
No logic implemented yet — all core methods raise NotImplementedError.
Establishes the full directory layout matching the architecture in CLAUDE.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

fellowship/llm/client.py

@@ -0,0 +1,62 @@
+"""
+LLM client — the only module that communicates with the LLM backend.
+Uses the OpenAI-compatible chat completions API via httpx.
+All other modules call this; nothing else touches the LLM directly.
+"""
+
+import logging
+from typing import AsyncIterator, Optional
+
+import httpx
+
+from fellowship.config import settings
+
+logger = logging.getLogger(__name__)
+
+# Retry config
+MAX_RETRIES = 1
+RETRY_DELAY = 2.0  # seconds
+
+
+class LLMClient:
+    def __init__(
+        self,
+        base_url: Optional[str] = None,
+        api_key: Optional[str] = None,
+    ) -> None:
+        self.base_url = (base_url or settings.llm_base_url).rstrip("/")
+        self.api_key = api_key or settings.llm_api_key
+
+    async def chat(
+        self,
+        model: str,
+        messages: list[dict],
+        temperature: Optional[float] = None,
+        max_tokens: Optional[int] = None,
+        tools: Optional[list[dict]] = None,
+    ) -> dict:
+        """
+        Send a chat completion request. Returns the full response dict.
+        Retries once on failure before raising.
+        """
+        raise NotImplementedError
+
+    async def chat_stream(
+        self,
+        model: str,
+        messages: list[dict],
+        temperature: Optional[float] = None,
+        max_tokens: Optional[int] = None,
+    ) -> AsyncIterator[str]:
+        """
+        Send a streaming chat completion request.
+        Yields content tokens as they arrive.
+        Only used when stream_tokens is enabled.
+        """
+        raise NotImplementedError
+
+    def _headers(self) -> dict[str, str]:
+        return {
+            "Authorization": f"Bearer {self.api_key}",
+            "Content-Type": "application/json",
+        }