fix(memory): unify Outcome enum and add ABANDONED support

- Add ABANDONED value to core Outcome enum in types.py
- Replace duplicate OutcomeType class in mcp/tools.py with alias to Outcome
- Simplify mcp/service.py to use outcome directly (no more silent mapping)
- Add migration 0006 to extend PostgreSQL episode_outcome enum
- Add missing constraints to migration 0005 (ix_facts_unique_triple_global)

This fixes the semantic issue where ABANDONED outcomes were silently
converted to FAILURE, losing information about task abandonment.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/alembic/versions/0005_add_memory_system_tables.py

@@ -300,6 +300,14 @@ def upgrade() -> None:
         unique=True,
         postgresql_where=sa.text("project_id IS NOT NULL"),
     )
+    # Unique constraint for global facts (project_id IS NULL)
+    op.create_index(
+        "ix_facts_unique_triple_global",
+        "facts",
+        ["subject", "predicate", "object"],
+        unique=True,
+        postgresql_where=sa.text("project_id IS NULL"),
+    )
 
     # =========================================================================
     # Create procedures table
@@ -396,6 +404,11 @@ def upgrade() -> None:
         "facts",
         "confidence >= 0.0 AND confidence <= 1.0",
     )
+    op.create_check_constraint(
+        "ck_facts_reinforcement_positive",
+        "facts",
+        "reinforcement_count >= 1",
+    )
 
     # Procedure constraints
     op.create_check_constraint(
@@ -476,11 +489,15 @@ def downgrade() -> None:
     # Drop check constraints first
     op.drop_constraint("ck_procedures_failure_positive", "procedures", type_="check")
     op.drop_constraint("ck_procedures_success_positive", "procedures", type_="check")
+    op.drop_constraint("ck_facts_reinforcement_positive", "facts", type_="check")
     op.drop_constraint("ck_facts_confidence_range", "facts", type_="check")
     op.drop_constraint("ck_episodes_tokens_positive", "episodes", type_="check")
     op.drop_constraint("ck_episodes_duration_positive", "episodes", type_="check")
     op.drop_constraint("ck_episodes_importance_range", "episodes", type_="check")
 
+    # Drop unique indexes for global facts
+    op.drop_index("ix_facts_unique_triple_global", "facts")
+
     # Drop tables in reverse order (dependencies first)
     op.drop_table("memory_consolidation_log")
     op.drop_table("procedures")

backend/app/alembic/versions/0006_add_abandoned_outcome.py

@@ -0,0 +1,52 @@
+"""Add ABANDONED to episode_outcome enum
+
+Revision ID: 0006
+Revises: 0005
+Create Date: 2025-01-06
+
+This migration adds the 'abandoned' value to the episode_outcome enum type.
+This allows episodes to track when a task was abandoned (not completed,
+but not necessarily a failure either - e.g., user cancelled, session timeout).
+"""
+
+from collections.abc import Sequence
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "0006"
+down_revision: str | None = "0005"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    """Add 'abandoned' value to episode_outcome enum."""
+    # PostgreSQL ALTER TYPE ADD VALUE is safe and non-blocking
+    op.execute("ALTER TYPE episode_outcome ADD VALUE IF NOT EXISTS 'abandoned'")
+
+
+def downgrade() -> None:
+    """Remove 'abandoned' from episode_outcome enum.
+
+    Note: PostgreSQL doesn't support removing values from enums directly.
+    This downgrade converts any 'abandoned' episodes to 'failure' and
+    recreates the enum without 'abandoned'.
+    """
+    # Convert any abandoned episodes to failure first
+    op.execute("""
+        UPDATE episodes
+        SET outcome = 'failure'
+        WHERE outcome = 'abandoned'
+    """)
+
+    # Recreate the enum without abandoned
+    # This is complex in PostgreSQL - requires creating new type, updating columns, dropping old
+    op.execute("ALTER TYPE episode_outcome RENAME TO episode_outcome_old")
+    op.execute("CREATE TYPE episode_outcome AS ENUM ('success', 'failure', 'partial')")
+    op.execute("""
+        ALTER TABLE episodes
+        ALTER COLUMN outcome TYPE episode_outcome
+        USING outcome::text::episode_outcome
+    """)
+    op.execute("DROP TYPE episode_outcome_old")