feat(cli): render uptime in human units

The UPTIME column printed raw seconds, so a server up for three hours
read as 10549s. Format the two largest non-zero units instead, dropping
the smaller one when it is zero: 49s, 12m 4s, 2h 55m, 6d 3h.

Days is the largest unit and the output never exceeds eight characters,
so the ten-wide column still holds and RESTARTS stays put.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01D9BWMXKKNpid7XM6oFbyYq

crates/xy/src/cli/format.rs

@@ -7,10 +7,7 @@ pub fn list_table(rows: &[ServerSummary]) -> String {
 
     for r in rows {
         let pid = r.pid.map(|p| p.to_string()).unwrap_or_else(|| "-".into());
-        let up = r
-            .uptime_secs
-            .map(|s| format!("{}s", s))
-            .unwrap_or_else(|| "-".into());
+        let up = r.uptime_secs.map(uptime).unwrap_or_else(|| "-".into());
 
         out.push_str(&format!(
             "{:<20}{:<12}{:<8}{:<8}{:<10}{}\n",
@@ -26,6 +23,28 @@ pub fn list_table(rows: &[ServerSummary]) -> String {
     out
 }
 
+fn uptime(secs: u64) -> String {
+    const MINUTE: u64 = 60;
+    const HOUR: u64 = 60 * MINUTE;
+    const DAY: u64 = 24 * HOUR;
+
+    let (major, minor, major_unit, minor_unit) = if secs >= DAY {
+        (secs / DAY, secs % DAY / HOUR, "d", "h")
+    } else if secs >= HOUR {
+        (secs / HOUR, secs % HOUR / MINUTE, "h", "m")
+    } else if secs >= MINUTE {
+        (secs / MINUTE, secs % MINUTE, "m", "s")
+    } else {
+        return format!("{secs}s");
+    };
+
+    if minor == 0 {
+        return format!("{major}{major_unit}");
+    }
+
+    format!("{major}{major_unit} {minor}{minor_unit}")
+}
+
 pub(crate) fn wait_line(info: &WaitInfo) -> String {
     format!(
         "  wait-for: {}\n            {}s elapsed, timeout {}s\n",
@@ -55,6 +74,62 @@ mod tests {
         assert!(out.contains("waiting"), "got: {out}");
     }
 
+    #[test]
+    fn uptime_under_a_minute_is_bare_seconds() {
+        assert_eq!(uptime(0), "0s");
+        assert_eq!(uptime(49), "49s");
+        assert_eq!(uptime(59), "59s");
+    }
+
+    #[test]
+    fn uptime_under_an_hour_is_minutes_and_seconds() {
+        assert_eq!(uptime(60), "1m");
+        assert_eq!(uptime(724), "12m 4s");
+        assert_eq!(uptime(3_599), "59m 59s");
+    }
+
+    #[test]
+    fn uptime_under_a_day_is_hours_and_minutes() {
+        assert_eq!(uptime(3_600), "1h");
+        assert_eq!(uptime(10_549), "2h 55m");
+        assert_eq!(uptime(86_399), "23h 59m");
+    }
+
+    #[test]
+    fn uptime_of_a_day_or_more_is_days_and_hours() {
+        assert_eq!(uptime(86_400), "1d");
+        assert_eq!(uptime(529_200), "6d 3h");
+        assert_eq!(uptime(2_707_200), "31d 8h");
+    }
+
+    #[test]
+    fn uptime_drops_a_trailing_zero_unit() {
+        assert_eq!(uptime(120), "2m");
+        assert_eq!(uptime(7_200), "2h");
+        assert_eq!(uptime(518_400), "6d");
+    }
+
+    #[test]
+    fn list_renders_uptime_in_human_units() {
+        let rows = vec![ServerSummary {
+            name: "vestige".to_string(),
+            state: ServerState::Running,
+            pid: Some(4821),
+            port: 3928,
+            uptime_secs: Some(10_549),
+            restart_count: 0,
+            last_exit: None,
+        }];
+
+        let out = list_table(&rows);
+
+        assert!(out.contains("2h 55m"), "got: {out}");
+        assert!(
+            !out.contains("10549"),
+            "raw seconds must not leak; got: {out}"
+        );
+    }
+
     #[test]
     fn status_renders_the_wait_condition_and_elapsed() {
         let info = WaitInfo {