nonblocking_index

Index sync must stay non-blocking for the host UI ( notably activity_bar and workspace_loading ).
Editor startup is gated by first_paint_startup; discovering a base must not construct Langium services, which are initialized lazily on the first parse.
While syncing, surface progress — state, processed / total, and the current file — in workspace_pane and index_panel.
In-flight sync must be cancellable from those surfaces; cancel keeps already-indexed rows and returns the index to ready.
Incremental behaviour ( see also indexing_incrementality ):
- Single-file create / change / delete via watchers indexes only that file — never a full base walk.
- Soft full sync ( `syncWorkspace` / Refresh ) skips parse + persist when the file's mtime matches the value stored on the documents row.
- Hard refresh ( `clearAndRebuildIndex` / Clear & rebuild ) wipes the store and reindexes every file.
Implemented by workspace-index.ts; editor adapter index-service.ts.

Status: done

Interactive page: nonblocking_index