Feature 4: sort tasks - incomplete first by position, completed by updated_at

- sort_tasks() extracts the sort logic into a standalone function
- Applied in load_tasks, App::new, check_initial_load, refresh_if_needed
- reorder_task guards: only NeedsAction tasks, never cross group boundary

src/app.rs

@@ -79,12 +79,13 @@ impl App {
         };
 
         let lists = db.get_lists();
-        let tasks = if !lists.is_empty() {
+        let mut tasks = if !lists.is_empty() {
             let list_id = &lists[0].id;
             db.get_tasks(list_id)
         } else {
             Vec::new()
         };
+        sort_tasks(&mut tasks);
 
         Self {
             lists,
@@ -162,7 +163,9 @@ impl App {
         if !lists.is_empty() && self.lists.is_empty() {
             self.lists = lists;
             if !self.lists.is_empty() {
-                self.tasks = self.db.get_tasks(&self.lists[0].id);
+                let mut tasks = self.db.get_tasks(&self.lists[0].id);
+                sort_tasks(&mut tasks);
+                self.tasks = tasks;
             }
         }
     }
@@ -172,7 +175,9 @@ impl App {
             self.last_sync_version = self.sync_stats.version;
             self.load_lists();
             if !self.lists.is_empty() && self.selected_list < self.lists.len() {
-                self.tasks = self.db.get_tasks(&self.lists[self.selected_list].id);
+                let mut tasks = self.db.get_tasks(&self.lists[self.selected_list].id);
+                sort_tasks(&mut tasks);
+                self.tasks = tasks;
             } else {
                 self.tasks.clear();
             }
@@ -739,13 +744,22 @@ impl App {
             return;
         }
 
-        let new_index = self.selected_task as i64 + direction;
+        let cur = self.selected_task;
+        if self.tasks[cur].status != TaskStatus::NeedsAction {
+            return;
+        }
+
+        let new_index = cur as i64 + direction;
         if new_index < 0 || new_index >= self.tasks.len() as i64 {
             return;
         }
 
-        let task_id = self.tasks[self.selected_task].id.clone();
-        let list_id = self.tasks[self.selected_task].list_id.clone();
+        if self.tasks[new_index as usize].status != TaskStatus::NeedsAction {
+            return;
+        }
+
+        let task_id = self.tasks[cur].id.clone();
+        let list_id = self.tasks[cur].list_id.clone();
 
         let new_pos = self.tasks[new_index as usize].position;
 
@@ -772,7 +786,9 @@ impl App {
 
     fn load_tasks(&mut self) {
         if self.selected_list < self.lists.len() {
-            self.tasks = self.db.get_tasks(&self.lists[self.selected_list].id);
+            let mut tasks = self.db.get_tasks(&self.lists[self.selected_list].id);
+            sort_tasks(&mut tasks);
+            self.tasks = tasks;
         } else {
             self.tasks.clear();
         }
@@ -784,6 +800,18 @@ impl App {
     }
 }
 
+fn sort_tasks(tasks: &mut Vec<Task>) {
+    tasks.sort_by(|a, b| match (&a.status, &b.status) {
+        (TaskStatus::NeedsAction, TaskStatus::Completed) => std::cmp::Ordering::Less,
+        (TaskStatus::Completed, TaskStatus::NeedsAction) => std::cmp::Ordering::Greater,
+        (TaskStatus::NeedsAction, TaskStatus::NeedsAction) => a.position.cmp(&b.position),
+        (TaskStatus::Completed, TaskStatus::Completed) => b
+            .updated_at
+            .unwrap_or(chrono::NaiveDateTime::MIN)
+            .cmp(&a.updated_at.unwrap_or(chrono::NaiveDateTime::MIN)),
+    });
+}
+
 fn uuid_v4() -> String {
     use std::time::{SystemTime, UNIX_EPOCH};
     let now = SystemTime::now()