agent: golden P2B — controller container gets /mnt:rslave + /mnt made rshared

build-golden.sh bootstrap makes /mnt a shared mount and binds it :rslave into the
controller container so enrolled data drives (and P3 self-heal remounts) propagate
in. Scoped to /mnt (Model A: only felhom-data-namespace mounts). Spike-proven.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

configs/build-golden.sh

@@ -126,16 +126,24 @@ docker rm -f felhom-controller >/dev/null 2>&1 || true
 # creates empty dirs → every bind-mounted stack (base infra AND customer apps) breaks. A named volume
 # would NOT fix this (it resolves to /var/lib/docker/volumes/...). Pre-create the dir, then same-path bind.
 mkdir -p /opt/docker/stacks
-# slice 8C: the controller is DE-PRIVILEGED — disk execution (scan/format/mount/migrate) is the
-# host agent's job now, so this run grants NO disk privileges: no --privileged, no /dev, no
-# /etc/fstab, no rshared /mnt. Only the bootstrap config (ro), the data volume, the stacks dir
-# (same-path host bind), and the docker socket (app/stack management). The controller reaches the
-# agent's local API for disk management.
+# slice 10 P2: the controller must SEE enrolled external data drives, which the agent binds into the
+# guest at /mnt/<name>. Make /mnt a SHARED mount so those binds (and later host-remount self-heal)
+# propagate into the controller container, then bind /mnt :rslave (host->container propagation ONLY —
+# the container can't mutate the guest mount tree). This is the ONE bind the 8C de-privileging left
+# out; scoped to /mnt, which (Model A) holds only Felhom's felhom-data-namespace mounts, never the
+# customer's other on-drive data. rbind preserves existing submounts; re-running re-shares (safe).
+mkdir -p /mnt
+mountpoint -q /mnt || mount --rbind /mnt /mnt
+mount --make-rshared /mnt
+# Otherwise still DE-PRIVILEGED: disk EXECUTION (scan/format/mount) stays the agent's — NO --privileged,
+# no /dev, no /etc/fstab. Bootstrap config (ro), data volume, stacks dir (same-path), the /mnt :rslave
+# view, and the docker socket. The controller reaches the agent's local API for disk management.
 docker run -d --name felhom-controller --restart unless-stopped "${HOSTNAME_ARGS[@]}" \
   -e FELHOM_BOOTSTRAP_PATH=/etc/felhom-bootstrap/bootstrap.json \
   -v /etc/felhom-bootstrap:/etc/felhom-bootstrap:ro \
   -v felhom-controller-data:/opt/docker/felhom-controller \
   -v /opt/docker/stacks:/opt/docker/stacks \
+  -v /mnt:/mnt:rslave \
   -v /var/run/docker.sock:/var/run/docker.sock \
   "$IMAGE"
 echo "[ctrl-bootstrap] controller started"