0b2605c5a8
Belt (ensureUserdataMounts) + FileBrowser sync skip ensure/mount when an external drive root is not a live mountpoint -> no 'mkdir userdata: permission denied' + no rootfs-shadow during a drive-absent window. System/local path never gated. Reuses system.IsMountPoint; matches planDriveGates external-only rule. T1-T4 + red-proofs. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>