huskies: merge 1144 story Gateway trampoline-restart: detached helper survives the gateway's own death

server/src/cli.rs

@@ -35,6 +35,11 @@ pub(crate) struct CliArgs {
     /// `HUSKIES_BINARY_SOURCE` env var, then derives the URL from
     /// `HUSKIES_UPSTREAM_GATEWAY`.
     pub(crate) upgrade_source: Option<String>,
+    /// Path to a trampoline job file (`--trampoline <path>`).
+    ///
+    /// When set, the binary runs as a detached trampoline helper: it kills the
+    /// old gateway, starts the new one, polls its health, and rolls back on failure.
+    pub(crate) trampoline: Option<String>,
 }
 
 /// Parse CLI arguments into `CliArgs`, or exit early for `--help` / `--version`.
@@ -51,6 +56,7 @@ pub(crate) fn parse_cli_args(args: &[String]) -> Result<CliArgs, String> {
     let mut upstream_gateway: Option<String> = None;
     let mut upgrade = false;
     let mut upgrade_source: Option<String> = None;
+    let mut trampoline: Option<String> = None;
     let mut i = 0;
 
     while i < args.len() {
@@ -143,6 +149,16 @@ pub(crate) fn parse_cli_args(args: &[String]) -> Result<CliArgs, String> {
             a if a.starts_with("--source=") => {
                 upgrade_source = Some(a["--source=".len()..].to_string());
             }
+            "--trampoline" => {
+                i += 1;
+                if i >= args.len() {
+                    return Err("--trampoline requires a path".to_string());
+                }
+                trampoline = Some(args[i].clone());
+            }
+            a if a.starts_with("--trampoline=") => {
+                trampoline = Some(a["--trampoline=".len()..].to_string());
+            }
             a if a.starts_with('-') => {
                 return Err(format!("unknown option: {a}"));
             }
@@ -172,6 +188,7 @@ pub(crate) fn parse_cli_args(args: &[String]) -> Result<CliArgs, String> {
         upstream_gateway,
         upgrade,
         upgrade_source,
+        trampoline,
     })
 }