b9c204c69e
- Added `IndexedSessionStorage` with `SessionStorageBackend` for index-based storage reads.
- Removed `readTextSync` from the public `SessionStorage` API and sync backends.
- Changed Redis and SQL backends to warm `{size, mtimeMs}` metadata and read via `readTextSlices`.
- Added per-path write queues and `drain()` to serialize operations and surface first failures.