fix(docker): never exit the server unless something is known to restart it

#373 restarts the Compose container by exiting the server, which is right for
the shipped deployment: `restart: unless-stopped` relaunches it. The updater
verified that policy through the Docker socket and, when it could not (no
socket mounted), failed open and exited anyway. Failing open is the correct
choice for the GATE, where refusing would block every install without a
socket, but not for the kill: a container the daemon does not restart goes
down for good, with no UI left to recover it from. That is exactly the case a
plain `docker run` of this image without `--restart` produces, and the image
sets CODEMAN_IN_CONTAINER=1 itself, so it takes the container path.

The decision now happens server-side, where both the socket and the Compose
env are reachable, and rides down to the script as `--restart-by-exit 0|1`.
It is 1 when the Compose file declared `CODEMAN_RESTART_BY_EXIT=1` (added there
and only there, since that file is what sets the restart policy; the image ENV
deliberately does not) or when the daemon confirmed an auto-restart policy.
Otherwise the build still lands, the status becomes
`completed-needs-manual-restart` with the `docker restart` hint, and the
server keeps running. The shipped deployment is unchanged in effect: with the
socket it was already confirmed, and without it the declaration now covers it.

Also: a root-run `Start-Codeman.sh` (common on Unraid) created the
fingerprint baseline's `.codeman` directory before the container's first start
and left it root-owned, which the unprivileged server could then never write
its own state into. It is chowned to PUID:PGID when running as root.

Verified with a real image build of the merged tree (classic builder; this
box's BuildKit lacks buildx): runs as uid 1000, tsc/esbuild and the toolchain
present, the four CLIs at their pins, docker/.env absent, and `docker inspect
$HOSTNAME` returns the restart policy through the mounted socket as that user.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qg6bcATm1pNNY4kQWGwzgu

docs/docker-self-update.md

@@ -56,6 +56,7 @@ unchanged. The container path is a new `SupervisorKind`, not a new updater.
 | `codeman-node-modules`, `codeman-dist` volumes | Container-owned build artefacts, layered over the bind mount.        |
 | `CODEMAN_IN_CONTAINER=1`                       | Tells `detectSupervisor()` to restart by exiting.                    |
 | `restart: unless-stopped`                      | Turns that exit into a restart. Verified before every update.        |
+| `CODEMAN_RESTART_BY_EXIT=1`                    | The Compose file's declaration of that policy, so the updater may exit even with no Docker socket. |
 | Toolchain + devDependencies in the image       | Lets `npm install` and `npm run build` run inside the container.     |
 | `docker-env-applied.json`                      | Fingerprint baseline, written by `Start-Codeman.sh` on every start.  |
 
@@ -118,6 +119,14 @@ Before signalling the server, the updater asks the Docker daemon for its own
 container's restart policy. If it is `no`, the update is refused: applying it
 would take Codeman down and leave no UI to recover from.
 
+If the policy cannot be read at all (no Docker socket mounted) the update is
+still allowed, but the final step changes: the server exits only when the
+Compose file declared `CODEMAN_RESTART_BY_EXIT=1` (the shipped one does, because
+it is the file that sets `restart: unless-stopped`) or the daemon confirmed an
+auto-restart policy. Otherwise the build completes and the panel asks you to
+restart the container by hand. A container started by plain `docker run` with no
+restart policy therefore gets a staged update, never an outage.
+
 ### What the gate deliberately does not do
 
 Every unknown fails **open**:
@@ -127,6 +136,10 @@ Every unknown fails **open**:
 - An unreadable `.env`, an unreachable Docker socket, or a target tag whose files
   cannot be read all yield "no blocker" rather than a refusal.
 
+The one place an unknown does NOT fail open is the kill itself: with neither the
+Compose declaration nor a daemon answer, the updater stages the build and asks
+for a manual restart rather than exiting a server nothing may bring back.
+
 The gate catches a specific, detectable class of mistake; it is not a last line of
 defence. It is also re-evaluated server-side on `POST /api/system/update`, so
 hiding the button in the UI is a courtesy rather than the control.