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-drive/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "workspace-drive"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+publish = false
+
+[dependencies]
+feature-storage.workspace = true
+rusqlite.workspace = true
+serde = { workspace = true, features = ["derive"] }
+serde_json.workspace = true
+sha2.workspace = true
+thiserror.workspace = true
+uuid = { workspace = true, features = ["v7"] }
+# Staging cleanup recognizes this version's local filename protocol. Reinspect
+# local publication and durability before upgrading, even within a patch series.
+object_store = { version = "=0.13.2", default-features = false, features = ["fs"] }
+bytes.workspace = true
+futures.workspace = true
+tokio = { workspace = true, features = ["rt", "rt-multi-thread"] }
+
+[dev-dependencies]
+tempfile.workspace = true