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.

Cargo.lock

@@ -1966,6 +1966,12 @@ version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "df3b46402a9d5adb4c86a0cf463f42e19994e3ee891101b1841f30a545cb49a9"
 
+[[package]]
+name = "humantime"
+version = "2.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "15cdd26707701c53297e2fa6afb323d55fbc1d0810c3aec078ae3ef0424c3c15"
+
 [[package]]
 name = "hybrid-array"
 version = "0.4.10"
@@ -3024,6 +3030,32 @@ dependencies = [
  "url",
 ]
 
+[[package]]
+name = "object_store"
+version = "0.13.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "622acbc9100d3c10e2ee15804b0caa40e55c933d5aa53814cd520805b7958a49"
+dependencies = [
+ "async-trait",
+ "bytes",
+ "chrono",
+ "futures-channel",
+ "futures-core",
+ "futures-util",
+ "http",
+ "humantime",
+ "itertools",
+ "parking_lot",
+ "percent-encoding",
+ "thiserror 2.0.18",
+ "tokio",
+ "tracing",
+ "url",
+ "walkdir",
+ "wasm-bindgen-futures",
+ "web-time",
+]
+
 [[package]]
 name = "oid-registry"
 version = "0.7.1"
@@ -6559,6 +6591,24 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "workspace-drive"
+version = "0.1.0"
+dependencies = [
+ "bytes",
+ "feature-storage",
+ "futures",
+ "object_store",
+ "rusqlite",
+ "serde",
+ "serde_json",
+ "sha2 0.11.0",
+ "tempfile",
+ "thiserror 2.0.18",
+ "tokio",
+ "uuid",
+]
+
 [[package]]
 name = "writeable"
 version = "0.6.3"
@@ -6708,6 +6758,7 @@ dependencies = [
  "workdir",
  "worker",
  "worker-runtime",
+ "workspace-drive",
  "yoi",
  "zeroize",
 ]