feat(pilot): add outcome tracking columns to session_suggested_fixes

Phase 8 prep for the fix outcome banner. Adds:
- status (proposed|applied_success|applied_failed|applied_partial|dismissed)
- applied_at, verified_at (timestamps)
- partial_notes, failure_reason (engineer-provided context)
- ai_outcome_proposal (JSONB for AI [FIX_OUTCOME] marker payloads)

Backfills status='dismissed' from user_decision='dismissed'. status is
orthogonal to user_decision — outcome (did the fix work?) vs script-path.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/alembic/versions/6492ec8d2d5b_add_fix_outcome_tracking_columns_to_.py

@@ -0,0 +1,74 @@
+"""add fix outcome tracking columns to session_suggested_fixes
+
+Adds: status, applied_at, verified_at, partial_notes, failure_reason,
+ai_outcome_proposal.
+
+status is the outcome dimension (did the fix work?), orthogonal to the
+existing user_decision column (which script-path the engineer took).
+
+Revision ID: 6492ec8d2d5b
+Revises: f07010f17b01
+Create Date: 2026-04-23 18:32:38.609719
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+
+# revision identifiers, used by Alembic.
+revision: str = '6492ec8d2d5b'
+down_revision: Union[str, None] = 'f07010f17b01'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "session_suggested_fixes",
+        sa.Column("status", sa.String(length=20), nullable=False, server_default=sa.text("'proposed'")),
+    )
+    op.add_column(
+        "session_suggested_fixes",
+        sa.Column("applied_at", sa.DateTime(timezone=True), nullable=True),
+    )
+    op.add_column(
+        "session_suggested_fixes",
+        sa.Column("verified_at", sa.DateTime(timezone=True), nullable=True),
+    )
+    op.add_column(
+        "session_suggested_fixes",
+        sa.Column("partial_notes", sa.Text(), nullable=True),
+    )
+    op.add_column(
+        "session_suggested_fixes",
+        sa.Column("failure_reason", sa.Text(), nullable=True),
+    )
+    op.add_column(
+        "session_suggested_fixes",
+        sa.Column("ai_outcome_proposal", postgresql.JSONB(), nullable=True),
+    )
+    # Backfill before constraint creation so dismissed rows satisfy the new CHECK.
+    op.execute(
+        "UPDATE session_suggested_fixes "
+        "SET status = 'dismissed' "
+        "WHERE user_decision = 'dismissed'"
+    )
+    op.create_check_constraint(
+        "ck_session_suggested_fixes_status",
+        "session_suggested_fixes",
+        "status IN ('proposed', 'applied_success', 'applied_failed', 'applied_partial', 'dismissed')",
+    )
+    op.alter_column("session_suggested_fixes", "status", server_default=None)
+
+
+def downgrade() -> None:
+    op.drop_constraint("ck_session_suggested_fixes_status", "session_suggested_fixes", type_="check")
+    op.drop_column("session_suggested_fixes", "ai_outcome_proposal")
+    op.drop_column("session_suggested_fixes", "failure_reason")
+    op.drop_column("session_suggested_fixes", "partial_notes")
+    op.drop_column("session_suggested_fixes", "verified_at")
+    op.drop_column("session_suggested_fixes", "applied_at")
+    op.drop_column("session_suggested_fixes", "status")

backend/app/models/session_suggested_fix.py

@@ -35,6 +35,11 @@ class SessionSuggestedFix(Base):
             "'one_off', 'draft_template', 'build_template', 'dismissed')",
             name="ck_session_suggested_fixes_user_decision",
         ),
+        CheckConstraint(
+            "status IN ('proposed', 'applied_success', 'applied_failed', "
+            "'applied_partial', 'dismissed')",
+            name="ck_session_suggested_fixes_status",
+        ),
     )
 
     id: Mapped[uuid.UUID] = mapped_column(
@@ -65,6 +70,21 @@ class SessionSuggestedFix(Base):
         JSONB, nullable=True
     )
     user_decision: Mapped[str | None] = mapped_column(String(32), nullable=True)
+    # Outcome dimension — did the fix work? Orthogonal to user_decision.
+    status: Mapped[str] = mapped_column(
+        String(20), nullable=False, default="proposed"
+    )
+    applied_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )
+    verified_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )
+    partial_notes: Mapped[str | None] = mapped_column(Text, nullable=True)
+    failure_reason: Mapped[str | None] = mapped_column(Text, nullable=True)
+    ai_outcome_proposal: Mapped[dict[str, Any] | None] = mapped_column(
+        JSONB, nullable=True
+    )
     # Set when a newer suggested fix supersedes this one.
     superseded_at: Mapped[datetime | None] = mapped_column(
         DateTime(timezone=True), nullable=True