hive-agent: inline todo dispatch arms instead of a sub-match + unreachable!

per mara's review on #2679: replace the separate dispatch_todo sub-match
(with its trailing unreachable! arm) with four small handler functions
called directly from dispatch's existing match. same behavior, no
unreachable! left in the todo path.

hive-agent/src/todo_server.rs

@@ -165,10 +165,26 @@ fn dispatch(
     bus: &Bus,
 ) -> Response {
     match req {
-        Request::UpsertTodo { .. }
-        | Request::ClearTodo { .. }
-        | Request::ListTodos { .. }
-        | Request::MarkTodoDone { .. } => dispatch_todo(req, store, wake),
+        Request::UpsertTodo {
+            subsystem,
+            key,
+            summary,
+            source,
+        } => upsert_todo(
+            store,
+            wake,
+            &subsystem,
+            key.as_deref(),
+            &summary,
+            source.as_deref(),
+        ),
+        Request::ClearTodo {
+            subsystem,
+            key,
+            all,
+        } => clear_todo(store, &subsystem, key.as_deref(), all),
+        Request::ListTodos { subsystem } => list_todos(store, subsystem.as_deref()),
+        Request::MarkTodoDone { id } => mark_todo_done(store, id),
         Request::StoreReminder {
             message,
             timing,
@@ -221,61 +237,68 @@ 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
+/// `UpsertTodo` handler: writes/refreshes a todo row, logs the outcome, and
+/// fires `wake` on a new-or-changed upsert so the serve loop runs a turn.
+fn upsert_todo(
+    store: &Todos,
+    wake: &Notify,
+    subsystem: &str,
+    key: Option<&str>,
+    summary: &str,
+    source: Option<&str>,
+) -> Response {
+    match store.upsert(subsystem, key, summary, source) {
+        Ok((id, changed)) => {
+            tracing::debug!(%subsystem, ?key, id, changed, "todo upsert");
+            if changed {
+                wake.notify_one();
             }
-            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),
+            Response::Ok
+        }
+        Err(e) => err(&e),
+    }
+}
+
+/// `ClearTodo` handler: drops one keyed todo, or every todo in `subsystem`
+/// when `all` is set.
+fn clear_todo(store: &Todos, subsystem: &str, key: Option<&str>, all: bool) -> Response {
+    let result = if all {
+        store.clear_subsystem(subsystem)
+    } else {
+        store.clear(subsystem, key)
+    };
+    match result {
+        Ok(count) => {
+            tracing::debug!(%subsystem, ?key, all, count, "todo clear");
+            Response::Acked {
+                count: u64::try_from(count).unwrap_or(0),
             }
         }
-        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),
+        Err(e) => err(&e),
+    }
+}
+
+/// `ListTodos` handler: read-only, so no debug logging — not relevant to
+/// diagnosing wake behaviour.
+fn list_todos(store: &Todos, subsystem: Option<&str>) -> Response {
+    match store.list(subsystem) {
+        Ok(todos) => Response::LooseEnds {
+            loose_ends: todos.into_iter().map(to_loose_end).collect(),
         },
-        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),
+    }
+}
+
+/// `MarkTodoDone` handler: marks a single todo done by id.
+fn mark_todo_done(store: &Todos, id: i64) -> Response {
+    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"),
+        }
+        Err(e) => err(&e),
     }
 }