slice 8C Phase A: agent disk endpoints + data-bearing classifier gate + mkfs (v0.12.0)

internal/storage: mkfs executor (Format, device-pinned, narrow FELHOM_FORMAT
sudoers) + data-bearing device inspection (InspectDevice/DeviceProbe via
blkid+lsblk; conservative — ambiguous=data-bearing). internal/localapi: /disks
(+ data-bearing flag), /disks/assign (EnsureMount), /disks/eject (Unmount +
dependent guests), /disks/format. SECURITY CENTERPIECE: the agent inspects the
device itself; data-bearing format -> ClassStorageWipe gate -> pending_signature
refused; the caller's claim is never trusted. Additive (no controller change yet).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

configs/felhom-agent.sudoers

@@ -36,4 +36,15 @@ Cmnd_Alias FELHOM_PROVISION = \
   /usr/bin/chown -R 100000\:100000 /var/lib/felhom-agent/guests/*, \
   /usr/sbin/pct set [0-9]* -mp[0-9]* /var/lib/felhom-agent/guests/*
 
-felhom-agent ALL=(root) NOPASSWD: FELHOM_MOUNT, FELHOM_DISK, FELHOM_PROVISION
+# Disk inspection + format (slice 8C). blkid/lsblk read the device's data-bearing evidence (the
+# agent decides data-bearing-ness from THIS, never the caller's claim); mkfs.* formats a device the
+# agent already classified blank (a data-bearing format is refused pending an operator signature).
+# The agent fine-validates the device path (ValidateBlockDevice: raw disk / partition under /dev
+# only) + fstype before any exec — the wildcard is the coarse allowlist, the agent is the fine gate.
+Cmnd_Alias FELHOM_FORMAT = \
+  /usr/sbin/blkid -p -o export /dev/*, \
+  /usr/bin/lsblk -J -o NAME,FSTYPE,PTTYPE,MOUNTPOINT /dev/*, \
+  /usr/sbin/mkfs.ext4 -F /dev/*, \
+  /usr/sbin/mkfs.xfs -f /dev/*
+
+felhom-agent ALL=(root) NOPASSWD: FELHOM_MOUNT, FELHOM_DISK, FELHOM_PROVISION, FELHOM_FORMAT