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/core/session.py

@@ -0,0 +1,76 @@
+"""
+Session data model — the single source of truth for a session's state.
+All other core modules read from and write to a Session instance.
+"""
+
+from dataclasses import dataclass, field
+from enum import Enum
+from typing import Any, Optional
+
+
+class ParticipationMode(str, Enum):
+    AUTONOMOUS = "autonomous"
+    REACTIVE = "reactive"
+    COLLABORATIVE = "collaborative"
+
+
+class TurnOrder(str, Enum):
+    ROUND_ROBIN = "round_robin"
+    ORCHESTRATED = "orchestrated"
+
+
+class SessionState(str, Enum):
+    WAITING = "waiting"       # Waiting for first talker message (reactive/collaborative)
+    RUNNING = "running"       # Loop is active
+    PAUSED = "paused"         # Paused via API
+    ENDED = "ended"           # Session is over
+
+
+@dataclass
+class BotConfig:
+    name: str
+    system_prompt: str
+    model: Optional[str] = None
+    temperature: Optional[float] = None
+    role: Optional[str] = None
+
+
+@dataclass
+class Message:
+    role: str                   # "bot", "talker", "system"
+    sender: str                 # bot name or talker display name
+    content: Optional[str]      # None while a rectification slot is reserved
+    turn: int
+    tokens: Optional[int] = None
+
+
+@dataclass
+class SessionOptions:
+    participation_mode: ParticipationMode = ParticipationMode.AUTONOMOUS
+    turn_order: TurnOrder = TurnOrder.ROUND_ROBIN
+    max_talkers: int = 1
+    max_turns: Optional[int] = None
+    max_time: Optional[int] = None
+    max_context_tokens: Optional[int] = None
+    rectify_history: bool = True
+    summarize_context: bool = False
+    stream_tokens: bool = False
+    goal: Optional[str] = None
+    debug: bool = False
+    llm_base_url: Optional[str] = None
+    llm_api_key: Optional[str] = None
+
+
+@dataclass
+class Session:
+    token: str
+    bots: list[BotConfig]
+    options: SessionOptions
+    global_system_prompt: Optional[str] = None
+    state: SessionState = SessionState.WAITING
+    history: list[Message] = field(default_factory=list)
+    turn_count: int = 0
+    robin_index: int = 0        # Current position in round_robin order
+    created_at: float = 0.0     # Unix timestamp
+    talker_count: int = 0
+    observer_count: int = 0