refactor: normalize script_builder_messages into separate table

Extract JSONB messages array from script_builder_sessions into a proper
script_builder_messages table with individual columns for role, content,
script, tokens, etc. Migration handles data migration from JSONB to rows.

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

backend/alembic/versions/064_normalize_script_builder_messages.py

@@ -0,0 +1,128 @@
+"""normalize script builder messages
+
+Revision ID: 064
+Revises: 063
+Create Date: 2026-03-21 22:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import UUID, JSONB
+
+
+# revision identifiers, used by Alembic.
+revision: str = '064'
+down_revision: Union[str, None] = '063'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # 1. Create the new script_builder_messages table
+    op.create_table(
+        'script_builder_messages',
+        sa.Column('id', UUID(as_uuid=True), primary_key=True),
+        sa.Column('session_id', UUID(as_uuid=True), sa.ForeignKey('script_builder_sessions.id', ondelete='CASCADE'), nullable=False, index=True),
+        sa.Column('role', sa.String(20), nullable=False, comment='user or assistant'),
+        sa.Column('content', sa.Text(), nullable=False),
+        sa.Column('script', sa.Text(), nullable=True, comment='Extracted script from AI response'),
+        sa.Column('script_filename', sa.String(200), nullable=True),
+        sa.Column('line_count', sa.Integer(), nullable=True),
+        sa.Column('input_tokens', sa.Integer(), nullable=True),
+        sa.Column('output_tokens', sa.Integer(), nullable=True),
+        sa.Column('created_at', sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
+    )
+
+    # 2. Migrate existing JSONB messages to the new table (if any exist)
+    conn = op.get_bind()
+    sessions = conn.execute(
+        sa.text("SELECT id, messages FROM script_builder_sessions WHERE messages IS NOT NULL AND messages != '[]'::jsonb")
+    ).fetchall()
+
+    for session_row in sessions:
+        session_id = session_row[0]
+        messages = session_row[1]
+        if not messages:
+            continue
+        for msg in messages:
+            conn.execute(
+                sa.text("""
+                    INSERT INTO script_builder_messages (id, session_id, role, content, script, script_filename, line_count, input_tokens, output_tokens, created_at)
+                    VALUES (gen_random_uuid(), :session_id, :role, :content, :script, :script_filename, :line_count, :input_tokens, :output_tokens, COALESCE(:timestamp::timestamptz, NOW()))
+                """),
+                {
+                    "session_id": session_id,
+                    "role": msg.get("role", "user"),
+                    "content": msg.get("content", ""),
+                    "script": msg.get("script"),
+                    "script_filename": msg.get("script_filename"),
+                    "line_count": msg.get("line_count"),
+                    "input_tokens": msg.get("input_tokens"),
+                    "output_tokens": msg.get("output_tokens"),
+                    "timestamp": msg.get("timestamp"),
+                },
+            )
+
+    # 3. Drop the old columns
+    op.drop_column('script_builder_sessions', 'messages')
+    op.drop_column('script_builder_sessions', 'message_count')
+
+
+def downgrade() -> None:
+    # 1. Re-add the JSONB columns
+    op.add_column('script_builder_sessions', sa.Column('messages', JSONB, nullable=False, server_default='[]'))
+    op.add_column('script_builder_sessions', sa.Column('message_count', sa.Integer(), nullable=False, server_default='0'))
+
+    # 2. Migrate data back from the messages table to JSONB
+    conn = op.get_bind()
+    sessions = conn.execute(
+        sa.text("SELECT DISTINCT session_id FROM script_builder_messages")
+    ).fetchall()
+
+    for (session_id,) in sessions:
+        messages = conn.execute(
+            sa.text("""
+                SELECT role, content, script, script_filename, line_count, input_tokens, output_tokens, created_at
+                FROM script_builder_messages
+                WHERE session_id = :session_id
+                ORDER BY created_at ASC
+            """),
+            {"session_id": session_id},
+        ).fetchall()
+
+        json_messages = []
+        user_count = 0
+        for msg in messages:
+            entry = {
+                "role": msg[0],
+                "content": msg[1],
+                "timestamp": msg[7].isoformat() if msg[7] else None,
+            }
+            if msg[2]:  # script
+                entry["script"] = msg[2]
+            if msg[3]:  # script_filename
+                entry["script_filename"] = msg[3]
+            if msg[4] is not None:  # line_count
+                entry["line_count"] = msg[4]
+            if msg[5] is not None:  # input_tokens
+                entry["input_tokens"] = msg[5]
+            if msg[6] is not None:  # output_tokens
+                entry["output_tokens"] = msg[6]
+            json_messages.append(entry)
+            if msg[0] == "user":
+                user_count += 1
+
+        import json
+        conn.execute(
+            sa.text("UPDATE script_builder_sessions SET messages = :messages::jsonb, message_count = :count WHERE id = :id"),
+            {"messages": json.dumps(json_messages), "count": user_count, "id": session_id},
+        )
+
+    # 3. Drop the messages table
+    op.drop_table('script_builder_messages')
+
+    # 4. Remove server defaults added for downgrade
+    op.alter_column('script_builder_sessions', 'messages', server_default=None)
+    op.alter_column('script_builder_sessions', 'message_count', server_default=None)