Bug: standalone updater retains every previous release (~1.8 GB after 8 updates)

Summary

On macOS (Apple Silicon), Codex's standalone updater keeps all prior full release directories under ~/.codex/packages/standalone/releases. There appears to be no automatic retention policy or cleanup, so normal updates continually grow the local Codex state.

Observed state

• Total ~/.codex size: 3.3 GB
• packages/standalone/releases: 2.1 GB
• Current release: 0.144.6-aarch64-apple-darwin
• Eight retained releases:
• 0.142.0, 0.142.2, 0.142.3, 0.142.4, 0.142.5 — ~242 MB each
• 0.144.1, 0.144.5, 0.144.6 — ~297 MB each
• Each release includes full binaries (the current bin directory is ~293 MB: codex ~248 MB plus codex-code-mode-host ~44 MB).

Keeping only the current release would reclaim approximately 1.8 GB in this installation.

Expected behavior

After a successful update and an appropriate rollback window, the updater should automatically prune old standalone releases (for example, retain the current release plus a small bounded number of previous releases), or expose a documented cleanup command/configuration.

Why this matters

Users can accumulate gigabytes of hidden application data through routine updates, with no clear indication that old full binaries are being retained. This is especially problematic on storage-constrained machines.

Please add bounded release retention / garbage collection, and document a safe cleanup path.