fix(db): widen ai_sessions.status column from varchar(20) to varchar(30)

'requesting_escalation' is 23 characters, exceeding the varchar(20)
limit. This caused a StringDataRightTruncationError 500 on escalate.

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

backend/alembic/versions/f0aad74ea51b_widen_ai_sessions_status_to_varchar_30.py

@@ -0,0 +1,36 @@
+"""widen ai_sessions status to varchar 30
+
+Revision ID: f0aad74ea51b
+Revises: b8d2f4a6c091
+Create Date: 2026-03-21 01:21:03.742028
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'f0aad74ea51b'
+down_revision: Union[str, None] = 'b8d2f4a6c091'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.alter_column(
+        "ai_sessions", "status",
+        type_=sa.String(30),
+        existing_type=sa.String(20),
+        existing_nullable=False,
+    )
+
+
+def downgrade() -> None:
+    op.alter_column(
+        "ai_sessions", "status",
+        type_=sa.String(20),
+        existing_type=sa.String(30),
+        existing_nullable=False,
+    )

backend/app/models/ai_session.py

@@ -85,7 +85,7 @@ class AISession(Base):
 
     # ── Session state ──
     status: Mapped[str] = mapped_column(
-        String(20), nullable=False, default="active", index=True,
+        String(30), nullable=False, default="active", index=True,
     )
     confidence_tier: Mapped[str] = mapped_column(
         String(20), nullable=False, default="discovery",