Add `DocumentStore::get_asset_by_workspace_path` trait method to `kebab-core` and implement it on `SqliteStore` via a private `asset_from_row` helper. Used by the incremental-ingest skip path to compare a freshly-computed blake3 checksum against the persisted row without a full round-trip through `put_asset_with_bytes`. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>