feat(sync): workspace-level git sync foundation with changeset staging

alembic/versions/b3f7a92d1c4e_add_rendered_files_to_workspace_sync_changesets.py

@@ -0,0 +1,36 @@
+"""add rendered files to workspace sync changesets
+
+Revision ID: b3f7a92d1c4e
+Revises: 25f4e2a1c9d8
+Create Date: 2026-06-07 00:00:00.000000
+
+"""
+
+from collections.abc import Sequence
+
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "b3f7a92d1c4e"
+down_revision: str | None = "25f4e2a1c9d8"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "workspace_sync_changeset",
+        sa.Column(
+            "rendered_files",
+            postgresql.JSONB(astext_type=sa.Text()),
+            server_default=sa.text("'{}'::jsonb"),
+            nullable=False,
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("workspace_sync_changeset", "rendered_files")