feat: Indexer: delete detection

Handle removed/trashed Drive items and prune Firestore docs.

Find the TypeScript indexer path that reads Drive items and writes them to Firestore, since the request is to handle removed/trashed items and prune stale docs. Start by reading the current item-status handling first, then add a delete branch so Firestore documents are removed when Drive reports an item as trashed/removed. Run the project’s relevant tests or integration checks for indexing, and verify that deleted or trashed Drive items disappear from Firestore after processing.

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