FIX: modify time not in index

.tsk/index

···
-tsk-10	foreign workspaces
-tsk-21	Add command to setup git stuff
-tsk-8	IMAP4-based sync
-tsk-17	Add reopen command
-tsk-16	Add ability to search archived tasks with find command
-tsk-15	Add link identification to tasks
-tsk-9	fix timestamp storage and parsing
-tsk-7	allow for creating tasks that don't go to top of stack
-tsk-13	user-defined labels
-tsk-18	Add reindex command
+tsk-21	Add command to setup git stuff	1732399520
+tsk-8	IMAP4-based sync	1728535307
+tsk-17	Add reopen command	1731441422
+tsk-16	Add ability to search archived tasks with find command	1731441422
+tsk-15	Add link identification to tasks	1731441422
+tsk-9	fix timestamp storage and parsing	1728534908
+tsk-10	foreign workspaces	1728534609
+tsk-7	allow for creating tasks that don't go to top of stack	1728426156
+tsk-13	user-defined labels	1728759002
+tsk-18	Add reindex command	1731441422

src/errors.rs

···
     #[allow(dead_code)]
     #[error("An unexpected error occurred: {0}")]
     Oops(Box<dyn std::error::Error>),
+    #[error("System time/clock error: {0}")]
+    SystemTime(#[from] std::time::SystemTimeError),
 }
 
 impl From<Infallible> for Error {

src/stack.rs

···
         self.file.seek(std::io::SeekFrom::Start(0))?;
         self.file.set_len(0)?;
         for item in self.all.iter() {
-            self.file.write_all(format!("{item}\n").as_bytes())?;
+            let time = item.modify_time.duration_since(UNIX_EPOCH)?.as_secs();
+            self.file.write_all(format!("{item}\t{}\n", time).as_bytes())?;
         }
         Ok(())
     }