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/api/models/session.py

@@ -0,0 +1,69 @@
+"""
+Pydantic request and response models for the session API endpoints.
+"""
+
+from typing import Optional
+from pydantic import BaseModel, Field
+
+from fellowship.core.session import (
+    BotConfig,
+    ParticipationMode,
+    TurnOrder,
+    SessionState,
+)
+
+
+class CreateSessionRequest(BaseModel):
+    bots: list[BotConfig] = Field(description="List of bots in this session")
+    global_system_prompt: Optional[str] = Field(
+        default=None, description="System prompt injected for all bots"
+    )
+    goal: Optional[str] = Field(
+        default=None,
+        description="Natural language goal. Required for orchestrator end_session tool to be available.",
+    )
+    participation_mode: ParticipationMode = Field(
+        default=ParticipationMode.AUTONOMOUS,
+        description="How human talkers interact with the session",
+    )
+    turn_order: TurnOrder = Field(
+        default=TurnOrder.ROUND_ROBIN,
+        description="How the next bot speaker is selected",
+    )
+    max_talkers: int = Field(default=1, description="Maximum simultaneous talker connections")
+    max_turns: Optional[int] = Field(default=None, description="End session after N bot turns")
+    max_time: Optional[int] = Field(default=None, description="End session after N seconds")
+    max_context_tokens: Optional[int] = Field(
+        default=None, description="End or summarize when total context reaches N tokens"
+    )
+    rectify_history: bool = Field(default=True, description="Enable history rectification")
+    summarize_context: bool = Field(
+        default=False, description="Summarize old context instead of ending when limit is reached"
+    )
+    stream_tokens: bool = Field(default=False, description="Stream bot responses token-by-token")
+    llm_base_url: Optional[str] = Field(
+        default=None, description="Override LLM backend URL for this session"
+    )
+    llm_api_key: Optional[str] = Field(
+        default=None, description="Override LLM API key for this session"
+    )
+    debug: Optional[bool] = Field(
+        default=None, description="Override debug mode for this session"
+    )
+
+
+class CreateSessionResponse(BaseModel):
+    token: str = Field(description="Session token used for all subsequent interactions")
+    state: SessionState
+    bot_count: int
+
+
+class SessionStatusResponse(BaseModel):
+    token: str
+    state: SessionState
+    bot_count: int
+    turn_count: int
+    talker_count: int
+    observer_count: int
+    participation_mode: ParticipationMode
+    turn_order: TurnOrder