feat: add SessionResolutionOutput model and register all 4 branching models

Introduces the session_resolution_outputs table for the three resolve
deliverables (psa_ticket_notes, knowledge_base, client_summary) with
UNIQUE(session_id, output_type) for safe upsert on regeneration.
Also registers SessionBranch, ForkPoint, SessionHandoff, and
SessionResolutionOutput in models/__init__.py so Alembic and the app
pick them up automatically.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/models/__init__.py

@@ -50,6 +50,10 @@ from .psa_activity_log import PsaActivityLog
 from .file_upload import FileUpload
 from .ai_session_embedding import AISessionEmbedding
 from .beta_feedback import BetaFeedback
+from .session_branch import SessionBranch
+from .fork_point import ForkPoint
+from .session_handoff import SessionHandoff
+from .session_resolution_output import SessionResolutionOutput
 
 __all__ = [
     "User",
@@ -114,4 +118,8 @@ __all__ = [
     "FileUpload",
     "AISessionEmbedding",
     "BetaFeedback",
+    "SessionBranch",
+    "ForkPoint",
+    "SessionHandoff",
+    "SessionResolutionOutput",
 ]

backend/app/models/session_resolution_output.py

@@ -0,0 +1,39 @@
+"""Session resolution output model — three deliverables generated on resolve."""
+import uuid
+from datetime import datetime, timezone
+from typing import Optional, Any
+
+from sqlalchemy import String, Text, DateTime, ForeignKey, CheckConstraint, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+from sqlalchemy.dialects.postgresql import UUID, JSONB
+
+from app.core.database import Base
+
+
+class SessionResolutionOutput(Base):
+    """One of three resolution deliverables: PSA ticket notes, KB article, client summary.
+    UNIQUE(session_id, output_type) + upsert so outputs can be regenerated.
+    """
+    __tablename__ = "session_resolution_outputs"
+    __table_args__ = (
+        CheckConstraint("output_type IN ('psa_ticket_notes', 'knowledge_base', 'client_summary')", name="ck_session_resolution_outputs_output_type"),
+        CheckConstraint("status IN ('draft', 'approved', 'pushed', 'rejected')", name="ck_session_resolution_outputs_status"),
+        UniqueConstraint("session_id", "output_type", name="uq_session_resolution_session_type"),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    session_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("ai_sessions.id", ondelete="CASCADE"), nullable=False, index=True)
+    output_type: Mapped[str] = mapped_column(String(30), nullable=False)
+    generated_content: Mapped[str] = mapped_column(Text, nullable=False)
+    structured_data: Mapped[Optional[dict[str, Any]]] = mapped_column(JSONB, nullable=True, comment="For KB: {symptoms, root_cause, steps, tags}")
+    edited_content: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+    status: Mapped[str] = mapped_column(String(20), nullable=False, default="draft")
+    pushed_to: Mapped[Optional[str]] = mapped_column(String(50), nullable=True)
+    pushed_at: Mapped[Optional[datetime]] = mapped_column(DateTime(timezone=True), nullable=True)
+    pushed_reference: Mapped[Optional[str]] = mapped_column(String(200), nullable=True)
+    generated_by_model: Mapped[str] = mapped_column(String(50), nullable=False)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=lambda: datetime.now(timezone.utc))
+    updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=lambda: datetime.now(timezone.utc), onupdate=lambda: datetime.now(timezone.utc))
+
+    # Relationships
+    session = relationship("AISession")