feat: add next_steps column and update session schemas

- Add next_steps TEXT column to sessions table via migration 034
- Add include_outcome_notes, include_next_steps, max_step_index to SessionExport
- Add next_steps to SessionUpdate, SessionResponse, SessionComplete

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/models/session.py

@@ -56,6 +56,9 @@ class Session(Base):
     scratchpad: Mapped[Optional[str]] = mapped_column(
         Text, nullable=True, server_default=sa.text("''")
     )
+    next_steps: Mapped[Optional[str]] = mapped_column(
+        Text, nullable=True, server_default=sa.text("''")
+    )
 
     # Relationships
     tree: Mapped["Tree"] = relationship("Tree", back_populates="sessions")

backend/app/schemas/session.py

@@ -50,6 +50,7 @@ class SessionUpdate(BaseModel):
     ticket_number: Optional[str] = Field(None, max_length=100)
     client_name: Optional[str] = Field(None, max_length=255)
     scratchpad: Optional[str] = None
+    next_steps: Optional[str] = None
     session_variables: Optional[dict[str, str]] = None
 
 
@@ -65,14 +66,15 @@ class SessionResponse(BaseModel):
     completed_at: Optional[datetime] = None
     outcome: Optional[SessionOutcome] = None
     outcome_notes: Optional[str] = None
+    next_steps: str = ""
     ticket_number: Optional[str] = None
     client_name: Optional[str] = None
     exported: bool
     scratchpad: str = ""
     session_variables: dict[str, str] = Field(default_factory=dict)
 
-    @validator('scratchpad', pre=True, always=True)
-    def normalize_scratchpad(cls, v):
+    @validator('scratchpad', 'next_steps', pre=True, always=True)
+    def normalize_text_fields(cls, v):
         return v or ""
 
     class Config:
@@ -83,11 +85,16 @@ class SessionExport(BaseModel):
     format: str = Field(default="markdown", pattern="^(text|markdown|html|psa)$")
     include_timestamps: bool = True
     include_tree_info: bool = True
+    # Phase A
+    include_outcome_notes: bool = True
+    include_next_steps: bool = True
+    max_step_index: Optional[int] = Field(None, ge=1, description="1-based inclusive step cutoff")
 
 
 class SessionComplete(BaseModel):
     outcome: SessionOutcome
     outcome_notes: Optional[str] = None
+    next_steps: Optional[str] = None
 
 
 class ScratchpadUpdate(BaseModel):