Function watchVolumeMountPoints

Watch the process-visible mount-point set for additions and removals.

This is a polling, eventually consistent state observer rather than a lossless mount-operation log. The caller controls the delay between polls with pollIntervalMs; it defaults to PollIntervalMsDefault (one minute). A new poll starts only after the prior poll has fully settled. timeoutMs bounds each caller-visible snapshot, but cannot cancel its underlying native or filesystem work; after a timeout, another poll is not scheduled until that raw work settles. On Linux, newly observed local paths receive a directory probe with one quarter of that snapshot budget.

Snapshots do not fetch capacity or accessibility status. On Linux, each newly observed local path (including the initial set) gets one directory probe to preserve the public directory-only mount-point behavior; remote paths are never probed, and raw timed-out probes must settle before another poll starts. On Windows, observation follows the current logical-drive-root enumeration and does not include directory-mounted volume paths. Because that shallow Windows enumeration does not query filesystem types, passing a custom systemFsTypes filter throws. Windows snapshots contain only mountPoint and the TypeScript-derived isSystemVolume; fields that require touching the drive, including fstype and isReadOnly, are omitted.

Existing mount points are returned by watcher.ready; they are not emitted as additions. A transient later polling error is available as lastError and through an error listener when one is registered, while the last good snapshot is retained.