Carry a service script, and declare the backend as a component

ai-server is now something Dev Updater can install, start and stop from
the phone: the project declares a Server component naming ./server/service,
and that script is where knowing about systemd and OpenRC lives.

Detection asks rather than looks -- `systemctl --user show-environment`
answering, or `rc-service --user` existing -- because a machine can carry
both binaries and an OpenRC below 0.60 has rc-service without --user.
Neither present is an error with a message, not a guess at a fallback.

Two things the script will not do. It never prompts: Dev Updater runs it
with stdin closed, so a sudo prompt would hang rather than fail, and
anything needing root exits telling you to run it yourself once. And on
OpenRC it refuses when XDG_RUNTIME_DIR is unset rather than proceeding --
user services store their state there, and the failure otherwise reads as
a broken service instead of a missing variable.

The server is declared before the app so it is built and delivered first;
a failed APK build then leaves the phone with the APK it already had
rather than half of a matched pair.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QQz6R4kBQcWSHBNZMgBnjL

app/.dev-updater.ron

@@ -3,9 +3,19 @@
 
 label: "AI Sessions",
 
+// The server is built and delivered before the APK: if the APK build then
+// fails, the phone keeps being offered the one it already had rather than
+// half of a matched pair.
 components: [
+    Server(
+        name: "backend",
+        build: "cargo build --release --manifest-path ../server/Cargo.toml",
+        // Installs into whichever user-service manager is here, and is how
+        // this server is started, stopped and asked about. See the script.
+        service: "../server/service",
+    ),
     Apk(
         name: "app",
         build: "./build-apk.sh",
     ),
-],
+]

server/service

@@ -0,0 +1,155 @@
+#!/bin/sh
+# Installs and controls ai-server as a user service, for Dev Updater to
+# drive from the phone -- and for you to drive by hand, which is the same
+# thing.
+#
+#   ./service install | uninstall | start | stop | restart | status
+#
+# `status` prints exactly one of `running`, `stopped` or `not-installed`
+# and exits 0. Anything else it prints, or any non-zero exit, means it
+# could not tell -- which the card shows as "couldn't check" rather than
+# as a service that is down.
+#
+# Nothing here ever prompts. Dev Updater runs this with stdin closed and no
+# terminal, so a `sudo` password prompt would not fail, it would hang until
+# the timeout with the card stuck mid-action. Anything needing root exits
+# with a message telling you to run it yourself once instead.
+#
+# User services on purpose: a system unit needs root to install, and a
+# build machine's own account is where a dev server belongs.
+set -eu
+
+SCRIPT_DIR=$(cd "$(dirname "$0")" && pwd)
+NAME=ai-server
+BINARY="$SCRIPT_DIR/target/release/$NAME"
+
+# Which init system is here, decided by asking rather than by looking for a
+# binary: a machine can carry both, and an OpenRC older than 0.60 has
+# rc-service but no --user at all.
+detect() {
+    if command -v systemctl >/dev/null 2>&1 &&
+        systemctl --user show-environment >/dev/null 2>&1; then
+        echo systemd
+    elif command -v rc-service >/dev/null 2>&1 &&
+        rc-service --user --help >/dev/null 2>&1; then
+        echo openrc
+    else
+        echo none
+    fi
+}
+
+MANAGER=$(detect)
+if [ "$MANAGER" = none ]; then
+    echo "No user-service manager here: this needs systemd with a user bus," >&2
+    echo "or OpenRC 0.60+ (older ones have no --user). Run $NAME by hand." >&2
+    exit 1
+fi
+
+# OpenRC keeps user-service state under XDG_RUNTIME_DIR and refuses without
+# it. Worth saying plainly: from a server started outside a login session
+# it can be unset, and the failure otherwise reads as a broken service
+# rather than a missing variable.
+if [ "$MANAGER" = openrc ] && [ -z "${XDG_RUNTIME_DIR:-}" ]; then
+    echo "XDG_RUNTIME_DIR is unset, and OpenRC stores user-service state in it." >&2
+    echo "Set it at login (elogind or pam_xdg) and try again." >&2
+    exit 1
+fi
+
+SYSTEMD_UNIT="${XDG_CONFIG_HOME:-$HOME/.config}/systemd/user/$NAME.service"
+OPENRC_UNIT="${XDG_CONFIG_HOME:-$HOME/.config}/rc/init.d/$NAME"
+
+installed() {
+    case "$MANAGER" in
+        systemd) [ -f "$SYSTEMD_UNIT" ] ;;
+        openrc) [ -f "$OPENRC_UNIT" ] ;;
+    esac
+}
+
+require_binary() {
+    [ -x "$BINARY" ] && return 0
+    echo "No built server at $BINARY -- build it first." >&2
+    exit 1
+}
+
+do_install() {
+    require_binary
+    case "$MANAGER" in
+        systemd)
+            mkdir -p "$(dirname "$SYSTEMD_UNIT")"
+            cat > "$SYSTEMD_UNIT" <<UNIT
+[Unit]
+Description=$NAME (installed by $SCRIPT_DIR/service)
+
+[Service]
+ExecStart=$BINARY
+Restart=on-failure
+WorkingDirectory=$SCRIPT_DIR
+
+[Install]
+WantedBy=default.target
+UNIT
+            systemctl --user daemon-reload
+            systemctl --user enable "$NAME" >/dev/null
+            ;;
+        openrc)
+            mkdir -p "$(dirname "$OPENRC_UNIT")"
+            cat > "$OPENRC_UNIT" <<UNIT
+#!/sbin/openrc-run
+name="$NAME"
+description="$NAME (installed by $SCRIPT_DIR/service)"
+command="$BINARY"
+command_background=true
+directory="$SCRIPT_DIR"
+pidfile="\${XDG_RUNTIME_DIR}/$NAME.pid"
+UNIT
+            chmod +x "$OPENRC_UNIT"
+            rc-update --user add "$NAME" >/dev/null
+            ;;
+    esac
+}
+
+do_uninstall() {
+    installed || return 0
+    case "$MANAGER" in
+        systemd)
+            systemctl --user disable --now "$NAME" >/dev/null 2>&1 || true
+            rm -f "$SYSTEMD_UNIT"
+            systemctl --user daemon-reload
+            ;;
+        openrc)
+            rc-service --user "$NAME" stop >/dev/null 2>&1 || true
+            rc-update --user del "$NAME" >/dev/null 2>&1 || true
+            rm -f "$OPENRC_UNIT"
+            ;;
+    esac
+}
+
+control() {
+    installed || { echo "$NAME is not installed" >&2; exit 1; }
+    case "$MANAGER" in
+        systemd) systemctl --user "$1" "$NAME" ;;
+        openrc) rc-service --user "$NAME" "$1" ;;
+    esac
+}
+
+case "${1:-}" in
+    install) do_install ;;
+    uninstall) do_uninstall ;;
+    start | stop | restart) control "$1" ;;
+    status)
+        if ! installed; then
+            echo not-installed
+        elif case "$MANAGER" in
+            systemd) systemctl --user --quiet is-active "$NAME" ;;
+            openrc) rc-service --user "$NAME" status >/dev/null 2>&1 ;;
+        esac then
+            echo running
+        else
+            echo stopped
+        fi
+        ;;
+    *)
+        echo "usage: $0 install|uninstall|start|stop|restart|status" >&2
+        exit 2
+        ;;
+esac