Bootstrap tree for the media box Linux conversion

Autoinstall lays down a thin base (sshd, key, DHCP, Docker CE, /srv) and hands
off to this repo on first boot. Everything interesting stays in git so it is
reviewable and re-runnable, rather than frozen onto a USB nobody can diff.

Stages, all idempotent:
  00-preflight  asserts hardware/BIOS state, changes nothing. Catches a BIOS
                update having silently re-enabled Secure Boot, which would stop
                the NVIDIA DKMS module loading on a box with no keyboard.
  10-secrets    ADD-ONLY seeder for /srv/secrets/stacks.env. Never overwrites an
                existing key. Verified against a pre-populated file: existing
                values, unrelated keys, the operator tier and existing manifest
                lines all survive byte-for-byte; a second run is a no-op.
  20-cifs       the 8 shares Plex actually uses (Share is excluded, it is not a
                library root). \040 escaping, nofail + x-systemd.automount +
                _netdev. Managed-block rewrite verified not to duplicate or to
                drop the root fstab entry.
  30-nvidia     nvidia-driver-580 explicitly: 580 is the LAST branch supporting
                Pascal, and the -open modules need Turing+. Pins against newer
                branches. Not in late-commands because DKMS needs the installed
                kernel, not the installer's.
  40-shell-mcp  builds the native MCP locally for amd64; refuses to finish
                unless /sse returns 401 without a token.
  50-plex       run by hand: PLEX_CLAIM expires in 4 minutes. Refuses to start
                against missing mounts and disables autoEmptyTrash, which with
                read-write NAS credentials is the most dangerous default here.

shell-mcp was built on arm64 originally. It builds clean on amd64 (whole dep
tree resolves to prebuilt manylinux x86_64 wheels, no compiler needed), but
dependencies are now pinned - the original installed mcp/starlette/uvicorn
unpinned and starlette has since gone 1.x. Port moved to 8103 so NPM host 42
can simply be repointed, and the tool description now says media box rather
than arrsstack.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

shell-mcp/docker-compose.yml

@@ -0,0 +1,22 @@
+services:
+  shell-mcp:
+    build:
+      context: .
+    image: shell-mcp:mediabox
+    container_name: shell-mcp
+    restart: unless-stopped
+    ports:
+      # Published on the LAN so NPM on arrsstack can reach 10.0.1.20:8103.
+      # No arrstack_arr_net here — that network lives on the Pi and does not
+      # exist on this host. The bearer token is the only gate on this port.
+      - "8103:8103"
+    environment:
+      - BEARER_TOKEN=${MEDIABOX_MCP_BEARER_TOKEN}
+      - PORT=8103
+      - TZ=${TZ:-America/New_York}
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+    # pid: host + privileged + nsenter --target 1 is what gives this container
+    # full root on the media box host, exactly as on arrsstack.
+    pid: host
+    privileged: true