fix: shell snapshot clean-up (#9155)

Clean all shell snapshot files corresponding to sessions that have not
been updated in 7 days
Those files should never leak. The only known cases were it can leak are
during non graceful interrupt of the process (`kill -9, `panic`, OS
crash, ...)

codex-rs/core/src/codex.rs

@@ -687,7 +687,7 @@ impl Session {
         // Create the mutable state for the Session.
         if config.features.enabled(Feature::ShellSnapshot) {
             default_shell.shell_snapshot =
-                ShellSnapshot::try_new(&config.codex_home, &default_shell)
+                ShellSnapshot::try_new(&config.codex_home, conversation_id, &default_shell)
                     .await
                     .map(Arc::new);
         }