hive-agent: report a failed mid-turn /compact instead of recording it as compacted

The turn-end /compact (operator button or the agent's `compact` tool) dropped
the compaction error with `let _ =`, emitted no note, and returned
`Ok(true)`, so the turn was recorded `result_kind = "compacted"` although
nothing compacted. The idle path already printed `/compact failed: …`.

Both paths now go through one `report_compact` helper that emits the done /
failed note; the turn-end path returns whether the compact succeeded.

docs/web-ui/agent.md

@@ -236,7 +236,8 @@ Slash commands today:
   `Bus::request_compact()` flag and returns immediately. The harness
   runs the `/compact` at the next turn boundary (end of the in-flight
   turn, or `turn::run_pending_compact` when idle); output streams into
-  the live panel. Works mid-turn, not only when idle.
+  the live panel. Works mid-turn, not only when idle. Either way the live
+  panel ends with a `/compact done` or `/compact failed: …` note.
 - `/model <name>` — `POST /api/model` flipping `Bus::set_model`.
   Takes effect on the next turn; persisted to
   `/state/hyperhive-model` so the override survives harness

hive-agent/src/turn.rs

@@ -155,7 +155,7 @@ pub async fn write_system_prompt(socket: &Path, label: &str) -> Result<PathBuf>
 /// One claude turn's outcome: `Ok(compacted)` on success, or a [`TurnError`]
 /// the serve loop must act on. The `compacted` bool is `true` when a
 /// compaction ran this turn (reactively on overflow, or proactively per the
-/// policy — or an operator `/compact` at turn end); it's recorded as
+/// policy — or a successful operator `/compact` at turn end); it's recorded as
 /// `result_kind = "compacted"` in turn stats so the stats page can distinguish
 /// those turns. Both `Ok(true)` and `Ok(false)` are ack'd; the error cases
 /// each map to a distinct serve-loop action (see [`emit_turn_end`] and the
@@ -461,7 +461,7 @@ pub async fn drive_turn(
         // Reflect `Compacting` in the UI like the idle path (`run_pending_compact`)
         // does; the serve loop resets to `Idle` once this turn returns.
         bus.set_state(crate::events::TurnState::Compacting);
-        let _ = session.compact(&config, &sink).await;
+        let compacted = report_compact(bus, session.compact(&config, &sink).await);
         // If the compact call asked to be woken (the agent's own `compact`
         // tool with a `wake_prompt`), stash it — the serve loop reads it
         // back after this turn returns and drives a synthetic follow-up
@@ -470,11 +470,31 @@ pub async fn drive_turn(
         if let Some(prompt) = request.wake_prompt {
             bus.set_post_compact_wake(prompt);
         }
-        return Ok(true);
+        return Ok(compacted);
     }
     outcome
 }
 
+/// Emit the `/compact done` / `/compact failed: …` note for a finished
+/// operator or agent `/compact` and return whether it succeeded. Shared by the
+/// turn-end path in [`drive_turn`] and the idle path in [`run_pending_compact`].
+fn report_compact<E: std::fmt::Display>(bus: &Bus, result: Result<(), E>) -> bool {
+    match result {
+        Ok(()) => {
+            bus.emit(LiveEvent::Note {
+                text: "/compact done".into(),
+            });
+            true
+        }
+        Err(e) => {
+            bus.emit(LiveEvent::Note {
+                text: format!("/compact failed: {e}"),
+            });
+            false
+        }
+    }
+}
+
 /// Pre-turn auto-reset check. If context is large AND the prompt cache has
 /// gone cold (idle time >= cache TTL), archive the current session so the
 /// next wake-up turn's `--resume <title>` misses and self-heals into a fresh
@@ -600,14 +620,7 @@ pub async fn run_pending_compact(files: &TurnFiles, bus: &Bus, session: &AgentSe
     bus.set_state(crate::events::TurnState::Compacting);
     let config = claude_config(bus, files);
     let sink = BusSink::new(bus);
-    match session.compact(&config, &sink).await {
+    report_compact(bus, session.compact(&config, &sink).await);
-        Ok(()) => bus.emit(LiveEvent::Note {
-            text: "/compact done".into(),
-        }),
-        Err(e) => bus.emit(LiveEvent::Note {
-            text: format!("/compact failed: {e}"),
-        }),
-    }
     bus.set_state(crate::events::TurnState::Idle);
     if let Some(prompt) = request.wake_prompt {
         bus.set_post_compact_wake(prompt);
@@ -821,8 +834,10 @@ fn archive_session(bus: &Bus, session: &AgentSession) {
 #[cfg(test)]
 mod tests {
     use super::{
-        PermissionAsk, TurnError, acp_permits, nonzero_or, parse_u64, runtime_error_to_turn,
+        PermissionAsk, TurnError, acp_permits, nonzero_or, parse_u64, report_compact,
+        runtime_error_to_turn,
     };
+    use crate::events::{Bus, LiveEvent};
     use hive_runtime::{AcpError, Error};
 
     #[test]
@@ -959,4 +974,31 @@ mod tests {
             Err(TurnError::Failed(_))
         ));
     }
+
+    fn compact_report(result: Result<(), &str>) -> (bool, Vec<String>) {
+        let bus = Bus::new();
+        let mut rx = bus.subscribe();
+        let ok = report_compact(&bus, result);
+        let mut notes = Vec::new();
+        while let Ok(ev) = rx.try_recv() {
+            if let LiveEvent::Note { text } = ev.event {
+                notes.push(text);
+            }
+        }
+        (ok, notes)
+    }
+
+    #[test]
+    fn a_failed_compact_is_reported_and_not_counted_as_compacted() {
+        let (compacted, notes) = compact_report(Err("spawn failed"));
+        assert!(!compacted);
+        assert_eq!(notes, ["/compact failed: spawn failed"]);
+    }
+
+    #[test]
+    fn a_successful_compact_is_reported_and_counted_as_compacted() {
+        let (compacted, notes) = compact_report(Ok(()));
+        assert!(compacted);
+        assert_eq!(notes, ["/compact done"]);
+    }
 }