v0.318.0: a part is offered for formatting only while nothing on its disk is mounted (agent 0.158.1 formattable)

The agent's root mkfs wrapper (security review of agent 0.158.0) refuses any mounted node and trusts no sibling claim; the
wizard now matches it. A free filesystem part of an in-use disk stays offered for use. Red-proved.

Claude-Session: https://claude.ai/code/session_012qRErfCoiTkvDK9N5XHbzb

controller/README.md

@@ -3404,15 +3404,16 @@ the controller only asks.
 - **Second copies** (v0.317.0): Tier-2 and the one-copy notice ask the agent (`POST /disks/same-disk`); a copy counts only on a
   proven different disk. **The whole-box backup offer** (v0.318.0, R-1084) does the same: proven different → the disk-failure
   promise; unproven (a VM) → offered without the promise (`backup.target.offer_unproven`); same disk → not offered.
-- **The internal data place „Belső tárhely"** (v0.318.0, agent ≥ 0.158.0): a volume on the system disk that the installer (or
+- **The internal data place „Belső tárhely"** (v0.318.0, agent ≥ 0.158.1): a volume on the system disk that the installer (or
   the operator's signed `add_internal_place`) makes on a one-disk box. When the agent reports it (`GET /disks`, kind
   `internal`), the drive-gate tick binds it into the guest and, on the next tick, registers it as a drive of kind `internal`
   — the default drive unless the household has one. Media and data-folder apps then install with no extra step. Eject,
   retire and format are refused (`err.web.belso_tarhely_eletciklus`); moving its data to another drive is allowed.
-- **Partitions** (v0.318.0, agent ≥ 0.158.0): the format and attach wizards list each part of a free disk — „format this
-  part" (empty, or with data through the typed confirmation) and „use this part" (an ext4/xfs filesystem). A disk whose other
-  part is already a drive offers only its free parts; formatting that whole disk is refused on the server too. No part is
-  ever created, deleted or resized from the dashboard (`16` D5).
+- **Partitions** (v0.318.0, agent ≥ 0.158.1): the format and attach wizards list each part of a free disk — „format this
+  part" (empty, or with data through the typed confirmation), only while nothing on the disk is mounted; „use this part"
+  (an ext4/xfs filesystem) always. A disk whose other part is already a drive offers only its free filesystem parts, for
+  use; formatting that whole disk is refused on the server too. No part is ever created, deleted or resized from the
+  dashboard (`16` D5).
 - **`/mnt/sys_drive` is never offered to attach** (v0.318.0, R-1082): it rides in every whole-box copy. A box that already
   registered it keeps it.