feat(01-02): create Project, Discussion, Round, Message, Consensus models

- Add Project model: id, name, created/updated_at, models (JSON), settings (JSON)
- Add Discussion model: id, project_id (FK), question, type, status, created_at
- Add Round model: id, discussion_id (FK), round_number, type
- Add Message model: id, round_id (FK), model, content, timestamp, is_direct
- Add Consensus model: id, discussion_id (FK unique), agreements, disagreements, generated_at/by
- Configure bidirectional relationships with cascade delete-orphan
- All FKs reference correct tables, all type hints present

src/moai/core/models.py

@@ -8,9 +8,16 @@ All IDs use UUID stored as String(36) for SQLite compatibility.
 Enums are stored as strings for database portability.
 """
 
-from enum import Enum
+from __future__ import annotations
 
-from sqlalchemy.orm import DeclarativeBase
+from datetime import datetime
+from enum import Enum
+from typing import Any
+from uuid import uuid4
+
+from sqlalchemy import JSON, DateTime, ForeignKey, String, Text
+from sqlalchemy import Enum as SAEnum
+from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, relationship
 
 
 class Base(DeclarativeBase):
@@ -38,3 +45,147 @@ class RoundType(str, Enum):
 
     PARALLEL = "parallel"
     SEQUENTIAL = "sequential"
+
+
+def _uuid() -> str:
+    """Generate a new UUID string."""
+    return str(uuid4())
+
+
+class Project(Base):
+    """A project container for related discussions.
+
+    Attributes:
+        id: Unique identifier (UUID).
+        name: Human-readable project name.
+        created_at: When the project was created.
+        updated_at: When the project was last modified.
+        models: List of AI model identifiers (e.g., ["claude", "gpt", "gemini"]).
+        settings: Configuration dict (default_rounds, consensus_threshold, system_prompt_override).
+        discussions: Related discussions in this project.
+    """
+
+    __tablename__ = "project"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=_uuid)
+    name: Mapped[str] = mapped_column(String(255))
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime, default=datetime.utcnow, onupdate=datetime.utcnow
+    )
+    models: Mapped[Any] = mapped_column(JSON, default=list)
+    settings: Mapped[Any] = mapped_column(JSON, default=dict)
+
+    discussions: Mapped[list[Discussion]] = relationship(
+        back_populates="project", cascade="all, delete-orphan"
+    )
+
+
+class Discussion(Base):
+    """A discussion within a project.
+
+    Attributes:
+        id: Unique identifier (UUID).
+        project_id: FK to parent project.
+        question: The question or topic being discussed.
+        type: Whether this is an "open" or "discuss" mode discussion.
+        status: Current status (active or completed).
+        created_at: When the discussion started.
+        project: Parent project relationship.
+        rounds: Discussion rounds.
+        consensus: Generated consensus (if any).
+    """
+
+    __tablename__ = "discussion"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=_uuid)
+    project_id: Mapped[str] = mapped_column(ForeignKey("project.id"))
+    question: Mapped[str] = mapped_column(Text)
+    type: Mapped[DiscussionType] = mapped_column(SAEnum(DiscussionType))
+    status: Mapped[DiscussionStatus] = mapped_column(
+        SAEnum(DiscussionStatus), default=DiscussionStatus.ACTIVE
+    )
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+
+    project: Mapped[Project] = relationship(back_populates="discussions")
+    rounds: Mapped[list[Round]] = relationship(
+        back_populates="discussion", cascade="all, delete-orphan"
+    )
+    consensus: Mapped[Consensus | None] = relationship(
+        back_populates="discussion", uselist=False, cascade="all, delete-orphan"
+    )
+
+
+class Round(Base):
+    """A round within a discussion.
+
+    Attributes:
+        id: Unique identifier (UUID).
+        discussion_id: FK to parent discussion.
+        round_number: Sequential round number within the discussion.
+        type: Whether this round is parallel or sequential.
+        discussion: Parent discussion relationship.
+        messages: Messages from AI models in this round.
+    """
+
+    __tablename__ = "round"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=_uuid)
+    discussion_id: Mapped[str] = mapped_column(ForeignKey("discussion.id"))
+    round_number: Mapped[int]
+    type: Mapped[RoundType] = mapped_column(SAEnum(RoundType))
+
+    discussion: Mapped[Discussion] = relationship(back_populates="rounds")
+    messages: Mapped[list[Message]] = relationship(
+        back_populates="round", cascade="all, delete-orphan"
+    )
+
+
+class Message(Base):
+    """A message from an AI model within a round.
+
+    Attributes:
+        id: Unique identifier (UUID).
+        round_id: FK to parent round.
+        model: AI model identifier (e.g., "claude", "gpt", "gemini").
+        content: The message content.
+        timestamp: When the message was created.
+        is_direct: True if this was a direct @mention to this model.
+        round: Parent round relationship.
+    """
+
+    __tablename__ = "message"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=_uuid)
+    round_id: Mapped[str] = mapped_column(ForeignKey("round.id"))
+    model: Mapped[str] = mapped_column(String(50))
+    content: Mapped[str] = mapped_column(Text)
+    timestamp: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+    is_direct: Mapped[bool] = mapped_column(default=False)
+
+    round: Mapped[Round] = relationship(back_populates="messages")
+
+
+class Consensus(Base):
+    """Generated consensus summary for a discussion.
+
+    Attributes:
+        id: Unique identifier (UUID).
+        discussion_id: FK to parent discussion (unique - one consensus per discussion).
+        agreements: List of bullet point strings for agreed items.
+        disagreements: List of {topic, positions: {model: position}} dicts.
+        generated_at: When the consensus was generated.
+        generated_by: Which model generated this summary.
+        discussion: Parent discussion relationship.
+    """
+
+    __tablename__ = "consensus"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=_uuid)
+    discussion_id: Mapped[str] = mapped_column(ForeignKey("discussion.id"), unique=True)
+    agreements: Mapped[Any] = mapped_column(JSON, default=list)
+    disagreements: Mapped[Any] = mapped_column(JSON, default=list)
+    generated_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+    generated_by: Mapped[str] = mapped_column(String(50))
+
+    discussion: Mapped[Discussion] = relationship(back_populates="consensus")