fix(supervisor): compute uptime at read time, not publish time

set_state computed uptime_secs from started_at.elapsed() and pushed the
result into the watch channel. do_start sets started_at immediately before
calling set_state(Running), so the published value was always ~0, and the
list/status handlers copied that frozen snapshot straight out. A server
that stayed healthy reported 0s forever, because the value was only
recomputed on the next state transition.

Status now carries started_at (an Instant, in-process only) and the
handlers derive uptime_secs when they build ServerSummary. The wire type
is unchanged.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EGntTHCW3sEPy1VBRopNNp

crates/xy-supervisor/src/supervisor.rs

@@ -48,7 +48,7 @@ pub struct Status {
     pub state: ServerState,
     pub pid: Option<u32>,
     pub port: u16,
-    pub uptime_secs: Option<u64>,
+    pub started_at: Option<Instant>,
     pub restart_count: u32,
     pub last_exit: Option<i32>,
 }
@@ -109,13 +109,11 @@ impl<S: Spawner> SupervisorTask<S> {
     }
 
     fn set_state(&mut self, s: ServerState) {
-        let uptime_secs = self.started_at.map(|t| t.elapsed().as_secs());
-
         let _ = self.status_tx.send(Status {
             state: s,
             pid: self.current_pid,
             port: self.cfg.port,
-            uptime_secs,
+            started_at: self.started_at,
             restart_count: self.restart_count,
             last_exit: self.last_exit,
         });
@@ -407,7 +405,7 @@ mod tests {
             state: ServerState::Stopped,
             pid: None,
             port: cfg.port,
-            uptime_secs: None,
+            started_at: None,
             restart_count: 0,
             last_exit: None,
         }

crates/xy/src/daemon/handlers.rs

@@ -170,7 +170,7 @@ async fn list(reg: &Registry) -> Result<Vec<ServerSummary>, ApiError> {
             state: s.state,
             pid: s.pid,
             port: s.port,
-            uptime_secs: s.uptime_secs,
+            uptime_secs: s.started_at.map(|t| t.elapsed().as_secs()),
             restart_count: s.restart_count,
             last_exit: s.last_exit,
         });
@@ -195,7 +195,7 @@ async fn status(reg: &Registry, name: &str) -> Result<StatusDetail, ApiError> {
             state: s.state,
             pid: s.pid,
             port: s.port,
-            uptime_secs: s.uptime_secs,
+            uptime_secs: s.started_at.map(|t| t.elapsed().as_secs()),
             restart_count: s.restart_count,
             last_exit: s.last_exit,
         },

crates/xy/src/daemon/mod.rs

@@ -43,7 +43,7 @@ pub fn spawn_supervisor(paths: &Paths, cfg: ServerConfig) -> Result<SupervisorHa
         state: ServerState::Stopped,
         pid: None,
         port: cfg.port,
-        uptime_secs: None,
+        started_at: None,
         restart_count: 0,
         last_exit: None,
     };

crates/xy/tests/uptime.rs

@@ -0,0 +1,40 @@
+mod common;
+use common::*;
+
+#[tokio::test]
+async fn uptime_grows_while_a_server_stays_running() {
+    let xy = xy_bin();
+    let sleeper = sleep_server_bin();
+    let mut h = Harness::new();
+    h.write_server("alpha", sleeper.to_str().unwrap(), 19_101, "always");
+    h.start_daemon(&xy).await;
+
+    for _ in 0..40 {
+        let (_c, out, _e) = h.run_cli(&xy, &["list"]).await;
+        if out.contains("alpha") && out.contains("running") {
+            break;
+        }
+        tokio::time::sleep(std::time::Duration::from_millis(100)).await;
+    }
+
+    tokio::time::sleep(std::time::Duration::from_millis(1_200)).await;
+
+    let (code, out, _e) = h.run_cli(&xy, &["list"]).await;
+
+    assert_eq!(code, 0);
+
+    let row = out
+        .lines()
+        .find(|l| l.starts_with("alpha"))
+        .unwrap_or_else(|| panic!("no alpha row in:\n{out}"));
+
+    let uptime = row
+        .split_whitespace()
+        .nth(4)
+        .unwrap_or_else(|| panic!("no uptime column in row: {row:?}"));
+
+    assert_ne!(
+        uptime, "0s",
+        "a server running for over a second must not report 0s uptime; row: {row:?}"
+    );
+}