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/store/session_store.py

@@ -0,0 +1,51 @@
+"""
+Session store — in-memory registry of all active sessions.
+Keyed by session token. Also holds the associated SessionLoop and MessageQueue per session.
+"""
+
+import logging
+import secrets
+from dataclasses import dataclass, field
+from typing import Optional
+
+from fellowship.core.session import Session
+from fellowship.core.loop import SessionLoop
+from fellowship.core.queue import MessageQueue
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class SessionEntry:
+    session: Session
+    loop: SessionLoop
+    queue: MessageQueue
+
+
+class SessionStore:
+    def __init__(self) -> None:
+        self._sessions: dict[str, SessionEntry] = {}
+
+    def create(self, session: Session, loop: SessionLoop, queue: MessageQueue) -> str:
+        """Register a new session. Returns the session token."""
+        self._sessions[session.token] = SessionEntry(session, loop, queue)
+        return session.token
+
+    def get(self, token: str) -> Optional[SessionEntry]:
+        """Return the SessionEntry for the given token, or None if not found."""
+        return self._sessions.get(token)
+
+    def remove(self, token: str) -> None:
+        """Remove a session from the store."""
+        self._sessions.pop(token, None)
+
+    def generate_token(self) -> str:
+        """Generate a cryptographically random session token."""
+        return secrets.token_urlsafe(32)
+
+    def all_tokens(self) -> list[str]:
+        return list(self._sessions.keys())
+
+
+# Global singleton — imported by routes and other modules
+session_store = SessionStore()