feat(drive): add durable Workspace document storage and lifecycle

Use object_store 0.13.2 immutable local blobs and FeatureStorage SQLite trees, revision CAS, same-transaction receipts, bounded reads/search, staged/orphan GC and retryable deletion. Attach Server authority to serialize cached Drive operations with deletion reservation. Document fsync compensation, Linux guarantees and offline DB-plus-blob restore.

Validation: root cargo check; workspace-drive 29 unit + 12 integration tests; feature-storage 13 tests; workspace-server 649 library + 11 binary tests with test-threads=4; cargo fmt --all -- --check; git diff --check HEAD. Default-parallel Server run hit the existing ticket_checker_burst timeout assertion (648 passed); the isolated filter and bounded-parallel full suite passed. Fault tests are not physical power-cut evidence.

crates/workspace-server/Cargo.toml

@@ -17,6 +17,7 @@ chrono = { version = "0.4", default-features = false, features = ["clock"] }
 futures.workspace = true
 config-source.workspace = true
 feature-storage.workspace = true
+workspace-drive.workspace = true
 subjektiv.workspace = true
 flow = { path = "../flow" }
 manifest.workspace = true