indexio_build_status bug: progress file only updates between sources, not during

indexio_build_status bug: progress file only updates between sources, not during. When a large source (e.g. fooof with many .py files) takes a long time, the status appears stuck. The _on_progress callback in the build worker script only writes when a source completes or starts.

Fix: add periodic updates within a source (e.g. every N files or every 30 seconds).

Related Notes

• issue-arash-20260326-174001-720656.md — Both relate to indexio infrastructure — missing MCP tools for index setup is directly adjacent to bugs in indexio build status reporting