fix(maestro): replace agent_session_id when a report names a new one

A resume issues a new conversation id, so write-once left the stored id
pointing at the pre-resume conversation and every later resume reattached
it. Rewrite the sidecar when the reported id differs from the stored one;
a repeated report of the same id still writes nothing.

Closes #176

crates/maestro-daemon/src/session.rs

@@ -1305,10 +1305,12 @@ impl SessionManager {
     /// and stays silent on the event stream at steady state.
     ///
     /// `agent_session_id` (#161) is the agent's own conversation id, parsed
-    /// by the caller from the hook payload's `session_id` field. It is
-    /// written once — the first report that carries one wins — and the
-    /// sidecar is only rewritten on that transition, never on every report,
-    /// since an agent's session id never changes mid-session.
+    /// by the caller from the hook payload's `session_id` field. The
+    /// sidecar is rewritten only when the reported id differs from the
+    /// stored one — a repeated report of the same id is pure churn from the
+    /// hook's `PreToolUse` cadence and writes nothing, but a resume (#176)
+    /// issues a new conversation id and must replace the stale one, or
+    /// every later resume reattaches the pre-resume conversation.
     pub async fn report_activity(
         &self,
         id: Uuid,
@@ -1330,16 +1332,16 @@ impl SessionManager {
                 state,
                 self.inner.report_ttl,
             ));
-            let newly_identified =
-                rec.session.agent_session_id.is_none() && agent_session_id.is_some();
-            if newly_identified {
+            let id_changed =
+                agent_session_id.is_some() && rec.session.agent_session_id != agent_session_id;
+            if id_changed {
                 rec.session.agent_session_id = agent_session_id;
                 self.inner
                     .sidecar
                     .write(&rec.session)
                     .map_err(SessionError::Sidecar)?;
             }
-            (changed || newly_identified).then(|| rec.session.clone())
+            (changed || id_changed).then(|| rec.session.clone())
         };
         if let Some(session) = updated {
             let _ = self

crates/maestro-daemon/tests/activity_report.rs

@@ -187,10 +187,30 @@ async fn a_reported_session_id_is_recorded_on_the_session() {
     assert_eq!(s.agent_session_id.as_deref(), Some("conv-abc123"));
 }
 
-/// #161: a session id does not change mid-session, so once set it is never
-/// overwritten by a later report — even one that names a different id.
+/// #161: repeated reports of the same id are pure churn from the hook's
+/// `PreToolUse` cadence — the sidecar must not be rewritten for them.
 #[tokio::test]
-async fn a_reported_session_id_is_written_once_and_never_replaced() {
+async fn a_repeated_report_of_the_same_session_id_writes_nothing() {
+    let fx = fixture(Duration::from_secs(300)).await;
+    let id = spawn_sleeping(&fx.manager).await;
+
+    fx.manager
+        .report_activity(id, ActivityState::Active, None, Some("conv-first".into()))
+        .await
+        .unwrap();
+    fx.manager
+        .report_activity(id, ActivityState::Active, None, Some("conv-first".into()))
+        .await
+        .unwrap();
+
+    let s = observed(&fx.manager, id).await;
+    assert_eq!(s.agent_session_id.as_deref(), Some("conv-first"));
+}
+
+/// #176: a resume issues a new conversation id. The stored id must move to
+/// it, or every later resume reattaches the stale pre-resume conversation.
+#[tokio::test]
+async fn a_reported_session_id_is_replaced_when_it_differs() {
     let fx = fixture(Duration::from_secs(300)).await;
     let id = spawn_sleeping(&fx.manager).await;
 
@@ -204,7 +224,14 @@ async fn a_reported_session_id_is_written_once_and_never_replaced() {
         .unwrap();
 
     let s = observed(&fx.manager, id).await;
-    assert_eq!(s.agent_session_id.as_deref(), Some("conv-first"));
+    assert_eq!(s.agent_session_id.as_deref(), Some("conv-second"));
+
+    let stored = fx
+        .sidecar
+        .read(id)
+        .expect("sidecar read")
+        .expect("sidecar present");
+    assert_eq!(stored.agent_session_id.as_deref(), Some("conv-second"));
 }
 
 #[tokio::test]