fix(install): use env vars for act_runner auto-registration

gitea/act_runner entrypoint auto-registers on first start using
GITEA_INSTANCE_URL and GITEA_RUNNER_REGISTRATION_TOKEN env vars,
then starts the daemon. Remove the separate register step entirely.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

install.sh

@@ -778,31 +778,18 @@ do_forgejo_runner_install() {
 
     mkdir -p "$FORGEJO_RUNNER_DIR"
 
-    log_step "Registering runner with Forgejo..."
-    docker run --rm \
-        -v "${FORGEJO_RUNNER_DIR}:/data" \
-        "${FORGEJO_RUNNER_IMAGE}" \
-        register \
-        --no-interactive \
-        --instance "${forgejo_url}" \
-        --token "${runner_token}" \
-        --name "$(hostname)-runner" \
-        --labels "ubuntu-latest:docker://node:20-bullseye,ubuntu-22.04:docker://node:20-bullseye"
-
-    if [ $? -ne 0 ]; then
-        log_err "Runner registration failed. Check the token and Forgejo URL."
-        return
-    fi
-    log_ok "Runner registered."
-
-    log_step "Starting Forgejo Runner..."
+    # gitea/act_runner auto-registers on first start via env vars, then starts daemon
+    log_step "Starting Forgejo Runner (auto-register on first boot)..."
     docker run -d \
         --name "${FORGEJO_RUNNER_CONTAINER}" \
         --restart unless-stopped \
+        -e GITEA_INSTANCE_URL="${forgejo_url}" \
+        -e GITEA_RUNNER_REGISTRATION_TOKEN="${runner_token}" \
+        -e GITEA_RUNNER_NAME="$(hostname)-runner" \
+        -e GITEA_RUNNER_LABELS="ubuntu-latest:docker://node:20-bullseye,ubuntu-22.04:docker://node:20-bullseye" \
         -v /var/run/docker.sock:/var/run/docker.sock \
         -v "${FORGEJO_RUNNER_DIR}:/data" \
-        "${FORGEJO_RUNNER_IMAGE}" \
-        daemon
+        "${FORGEJO_RUNNER_IMAGE}"
 
     log_ok "Forgejo Runner started."
     echo ""