API: Drive object, typed StreamUrl, tray lock/unlock, Send traits

- Rename DriveSession → Drive across entire codebase
- find_drives() returns Vec<Drive>, find_drive() returns Option<Drive>
- resolve_device() now pub(crate) — internal only
- StreamUrl is now a typed enum (Disc, Mkv, M2ts, Iso, Network, Stdio, Null)
  with scheme() and path_str() accessors, replacing struct of Strings
- Add lock_tray() / unlock_tray() for safe disc access during rips
- Improve reset() with eject cycle that clears LibreDrive stuck state
- Add Send bounds to ScsiTransport and PlatformDriver traits
- DiscOptions uses PathBuf instead of String for device/keydb paths
- Update doc example to use new Drive API

src/sector.rs

@@ -1,6 +1,6 @@
 //! SectorReader — trait for reading 2048-byte disc sectors.
 //!
-//! Implemented by DriveSession (SCSI) and IsoFile (file-backed).
+//! Implemented by Drive (SCSI) and IsoFile (file-backed).
 //! Used by UDF parser, disc scanner, label parsers — anything that
 //! reads sectors doesn't need to know where they come from.