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

CHANGELOG.md

@@ -1,7 +1,7 @@
 ## v0.318.0 — the internal data place, partitions, an honest whole-box backup offer, sys_drive never offered (2026-10-16)
 
 **MinAgent: 0.157.0** — nothing here calls a new agent endpoint. The internal place and the partitions appear only when the
-agent (≥ 0.158.0) reports them; below that the pages are exactly as before. The backup offer uses the 0.157.0 same-disk call
+agent (≥ 0.158.1; 0.158.0 is superseded) reports them; below that the pages are exactly as before. The backup offer uses the 0.157.0 same-disk call
 (`FeatureSameDisk`), and an older agent keeps today's offer. No golden (`09` §3 decision 250). Design: felhom.eu
 `architecture/16-storage-physical-identity.md` §4–§6 (build B; operator rulings D3–D5, sizes 2026-10-16).
 
@@ -15,10 +15,12 @@ agent (≥ 0.158.0) reports them; below that the pages are exactly as before. Th
   agent → today's offer.
 - **R-1082 — `/mnt/sys_drive` is never offered to attach** (operator ruling 2026-10-16 „hide it now"): excluded by device, so
   no second bind of the data volume can bring it back. A box that already registered it keeps it.
-- **Partitions** (`16` §6): the format and attach wizards list each part of a free disk („{n}. rész"); a disk whose other
-  part is a registered drive offers only its free parts, and formatting that whole disk is refused on the server too
-  (`err.web.meghajto_hasznalatban_formazas`). A formatted part's filesystem is found for the mount. Nothing creates, deletes
-  or resizes a part.
+- **Partitions** (`16` §6, agent ≥ 0.158.1): the format and attach wizards list each part of a free disk („{n}. rész").
+  A part is offered for FORMATTING only while nothing on its disk is mounted (the agent's `formattable`: its root mkfs
+  wrapper refuses any mounted node and trusts no „it is Felhom's own" claim — security review of agent 0.158.0). A disk
+  whose other part is a registered drive offers only its free filesystem parts, for USE; formatting that whole disk is
+  refused on the server too (`err.web.meghajto_hasznalatban_formazas`). A formatted part's filesystem is found for the
+  mount. Nothing creates, deletes or resizes a part.
 - Tests red-proved: internal_place_test.go, d4 (a media app lands on the internal place), r1084_offer_identity_test.go,
   r1082_sysdrive_hidden_test.go, partitions_test.go. Four parity fixtures refreshed (diff = only the new lines).