hive-agent: add debug logging around todo upsert/clear/mark-done

diagnostic instrumentation for #2678 (phantom 'you have todos' wakes
after clearing bash-task todos). logs subsystem/key/id/changed on
UpsertTodo, subsystem/key/all/count on ClearTodo, id/count on
MarkTodoDone, and a marker when the serve loop actually consumes a
todo_wake notification. no behavior change - RUST_LOG=debug only.

hive-agent/src/main.rs

@@ -585,7 +585,10 @@ async fn serve_loop<S: Surface>(
                 }
             } {
                 RecvOutcome::Message(first) => first,
-                RecvOutcome::LocalTodo => synthetic_todo_message(),
+                RecvOutcome::LocalTodo => {
+                    tracing::debug!("todo wake consumed, sending synthetic todo message");
+                    synthetic_todo_message()
+                }
                 RecvOutcome::Empty => {
                     // Idle: no message this poll. Service a queued operator
                     // `/compact` here so it runs even when no turn is driving

hive-agent/src/todo_server.rs

@@ -165,49 +165,10 @@ fn dispatch(
     bus: &Bus,
 ) -> Response {
     match req {
-        Request::UpsertTodo {
-            subsystem,
-            key,
-            summary,
-            source,
-        } => match store.upsert(&subsystem, key.as_deref(), &summary, source.as_deref()) {
-            Ok((_, changed)) => {
-                if changed {
-                    wake.notify_one();
-                }
-                Response::Ok
-            }
-            Err(e) => err(&e),
-        },
-        Request::ClearTodo {
-            subsystem,
-            key,
-            all,
-        } => {
-            let result = if all {
-                store.clear_subsystem(&subsystem)
-            } else {
-                store.clear(&subsystem, key.as_deref())
-            };
-            match result {
-                Ok(count) => Response::Acked {
-                    count: u64::try_from(count).unwrap_or(0),
-                },
-                Err(e) => err(&e),
-            }
-        }
-        Request::ListTodos { subsystem } => match store.list(subsystem.as_deref()) {
-            Ok(todos) => Response::LooseEnds {
-                loose_ends: todos.into_iter().map(to_loose_end).collect(),
-            },
-            Err(e) => err(&e),
-        },
-        Request::MarkTodoDone { id } => match store.mark_done(id) {
-            Ok(count) => Response::Acked {
-                count: u64::try_from(count).unwrap_or(0),
-            },
-            Err(e) => err(&e),
-        },
+        Request::UpsertTodo { .. }
+        | Request::ClearTodo { .. }
+        | Request::ListTodos { .. }
+        | Request::MarkTodoDone { .. } => dispatch_todo(req, store, wake),
         Request::StoreReminder {
             message,
             timing,
@@ -260,6 +221,64 @@ fn dispatch(
     }
 }
 
+/// Todo-family requests (loose-ends v2). `req` is guaranteed by [`dispatch`]
+/// to be one of the four todo variants; any other variant is a caller bug.
+fn dispatch_todo(req: Request, store: &Todos, wake: &Notify) -> Response {
+    match req {
+        Request::UpsertTodo {
+            subsystem,
+            key,
+            summary,
+            source,
+        } => match store.upsert(&subsystem, key.as_deref(), &summary, source.as_deref()) {
+            Ok((id, changed)) => {
+                tracing::debug!(subsystem = %subsystem, key = ?key, id, changed, "todo upsert");
+                if changed {
+                    wake.notify_one();
+                }
+                Response::Ok
+            }
+            Err(e) => err(&e),
+        },
+        Request::ClearTodo {
+            subsystem,
+            key,
+            all,
+        } => {
+            let result = if all {
+                store.clear_subsystem(&subsystem)
+            } else {
+                store.clear(&subsystem, key.as_deref())
+            };
+            match result {
+                Ok(count) => {
+                    tracing::debug!(subsystem = %subsystem, key = ?key, all, count, "todo clear");
+                    Response::Acked {
+                        count: u64::try_from(count).unwrap_or(0),
+                    }
+                }
+                Err(e) => err(&e),
+            }
+        }
+        Request::ListTodos { subsystem } => match store.list(subsystem.as_deref()) {
+            Ok(todos) => Response::LooseEnds {
+                loose_ends: todos.into_iter().map(to_loose_end).collect(),
+            },
+            Err(e) => err(&e),
+        },
+        Request::MarkTodoDone { id } => match store.mark_done(id) {
+            Ok(count) => {
+                tracing::debug!(id, count, "todo mark-done");
+                Response::Acked {
+                    count: u64::try_from(count).unwrap_or(0),
+                }
+            }
+            Err(e) => err(&e),
+        },
+        _ => unreachable!("dispatch only routes todo variants here"),
+    }
+}
+
 /// `Request::Compact` handler: gate on context usage, then queue the same
 /// deferred `compact_pending` flag the operator's `/compact` button sets.
 /// Mirrors `hive-agent::web_ui::actions::post_compact` but reachable from