hive-subagent-mcp: trim the running-status liveness clause

The 'Last event Ns ago' line used to repeat the full working-vs-wedged
explanation on every single status call. That's already covered by
the status tool's own MCP description and by docs/tools/subagent.md's
'Is it working, or is it wedged?' section, so restating it every call
was pure repetition on a line meant to be skimmed, possibly several
times a minute. Down to just the number and the state name.

hive-subagent-mcp/src/session.rs

@@ -1630,11 +1630,18 @@ pub fn status(state: &State, name: &str, dir: Option<&str>) -> anyhow::Result<St
     })
 }
 
-/// The liveness sentence appended to a *running* answer, and the whole point
+/// The liveness clause appended to a *running* answer, and the whole point
 /// of recording the timestamp: an age in seconds a caller can read a verdict
 /// off directly, rather than one it has to go and measure itself with `ps`
 /// and CPU-time deltas.
 ///
+/// Deliberately just the number now — the full "seconds means working,
+/// minutes means wedged, resets each turn" explanation used to repeat here
+/// on every single call. It already lives in the `status` tool description
+/// and in `docs/tools/subagent.md`'s "Is it working, or is it wedged?"
+/// section, so restating it in a line meant to be skimmed, possibly several
+/// times a minute, was pure repetition.
+///
 /// Empty when there's no age to report — a turn that ended between `status`
 /// reading `running` and reading the clock. Saying nothing is right there:
 /// the alternative is an age that describes a turn which has already
@@ -1642,13 +1649,7 @@ pub fn status(state: &State, name: &str, dir: Option<&str>) -> anyhow::Result<St
 fn describe_liveness(age: Option<Duration>) -> String {
     match age {
         None => String::new(),
-        Some(age) => format!(
+        Some(age) => format!(" Last event {}s ago.", age.as_secs()),
-            " Last event {}s ago — how long since this turn's claude process produced any output \
-             at all, whatever it was: a few seconds means it's working, an age that keeps \
-             climbing into the minutes means it's wedged. It resets at each turn's spawn, so on a \
-             goal run it describes the turn in flight, not the run.",
-            age.as_secs()
-        ),
     }
 }