Add task title editing/deletion, timeline click-to-open, widget app launch

Task-detail modal was description-only with no delete affordance;
HandleUpdateTask now saves the title too and a Delete button hits a new
DELETE /tasks/{id} route backed by store.DeleteNativeTask, which repairs
chain_position/unlocks the successor when the deleted task belongs to a
chain. Timeline tab task/card/gtask rows now open the same detail modal
as the Tasks tab. Android widget's "TODAY" header is now a tap target
that launches DashboardActivity, since nothing previously opened the
full app from the widget.

1 files changed, 61 insertions, 0 deletions

diff --git a/internal/store/native_tasks.go b/internal/store/native_tasks.go
index 11a9197..9d9af2c 100644
--- a/internal/store/native_tasks.go
+++ b/internal/store/native_tasks.go
@@ -161,6 +161,67 @@ func (s *Store) UpdateNativeTaskDescription(id, description string) error {
 	return err
 }
 
+// DeleteNativeTask permanently removes a task. Returns ErrNativeTaskNotFound
+// if id doesn't match any row. If the task belongs to a chain, this also
+// closes the resulting gap in chain_position (advanceChain looks up
+// chain_position+1, so a gap would either strand the chain mid-sequence or,
+// if the deleted task was the unlocked one, silently stop it from ever
+// advancing) and, if the deleted task was itself the unlocked position,
+// unlocks whatever now occupies that position -- or marks the chain
+// completed if nothing does (the deleted task was the last one left).
+func (s *Store) DeleteNativeTask(id string) error {
+	task, err := s.GetNativeTaskByID(id)
+	if err != nil {
+		return err
+	}
+
+	if task.ChainID == "" {
+		result, err := s.db.Exec(`DELETE FROM native_tasks WHERE id = ?`, id)
+		if err != nil {
+			return err
+		}
+		return checkRowsAffected(result)
+	}
+
+	tx, err := s.db.Begin()
+	if err != nil {
+		return err
+	}
+	defer func() { _ = tx.Rollback() }()
+
+	if _, err := tx.Exec(`DELETE FROM native_tasks WHERE id = ?`, id); err != nil {
+		return err
+	}
+	if _, err := tx.Exec(`
+		UPDATE native_tasks SET chain_position = chain_position - 1
+		WHERE chain_id = ? AND chain_position > ?
+	`, task.ChainID, task.ChainPosition); err != nil {
+		return err
+	}
+
+	if task.ChainUnlocked {
+		now := config.Now()
+		result, err := tx.Exec(`
+			UPDATE native_tasks SET chain_unlocked = 1, due_date = ?, updated_at = ?
+			WHERE chain_id = ? AND chain_position = ?
+		`, now, now, task.ChainID, task.ChainPosition)
+		if err != nil {
+			return err
+		}
+		successorPromoted, err := result.RowsAffected()
+		if err != nil {
+			return err
+		}
+		if successorPromoted == 0 {
+			if _, err := tx.Exec(`UPDATE task_chains SET status = 'completed' WHERE id = ?`, task.ChainID); err != nil {
+				return err
+			}
+		}
+	}
+
+	return tx.Commit()
+}
+
 // ErrChainTaskLocked is returned by CompleteNativeTask when the task
 // belongs to a chain but isn't the currently-unlocked position -- without
 // this guard, completing a locked task directly by id (bypassing the UI,