ADR-0024: Remove the non-elevated scope index

Date: 2026-07-26 / Status: Adopted

The folder-walk + ReadDirectoryChangesW fallback was removed. It duplicated scan, freshness, persistence, configuration, and onboarding while providing weaker coverage than the product’s defining NTFS $MFT + USN path.

Production indexing now has one model: an asInvoker UI talks to the on-demand service; an already-elevated --engine=inproc remains the development/recovery fallback. If the service is absent, the UI offers its one-time installation instead of building a second per-folder engine.

Scope exclusions go with it. They existed to prune the folder walk, and there is no longer a folder-walk ingest path to prune; excluding a path from results remains available where it always belonged, as query syntax. (This absorbs the separately recorded exclusion decision, which had no content of its own once the walk was gone.)