## Why
Configured Git marketplaces may be defined outside the user config, but those definitions could not download or update their snapshots.
## What changed
- Select marketplace source, ref, and sparse-path settings from the effective merged configuration for startup synchronization and explicit upgrades.
- Preserve the initiating operation's configuration loader and overrides when reloading before activation.
- Roll back activation if the marketplace definition changed or configuration can no longer be loaded, without copying settings into the user config.
## Testing
- Cover system-defined marketplaces, CLI overrides, startup fallback after invalid user configuration, and rollback after configuration changes.
GitOrigin-RevId: 53d1eecf68a91ce2aa8430e5749d78697bfcd821
## Why
Addresses #9274
Running `codex update` currently starts an interactive Codex session
with `update` as the prompt. That is a rough edge for users who expect a
direct self-update command after seeing the existing update notice, and
it forces them to copy the suggested package-manager command manually.
## What changed
- Added a top-level `codex update` subcommand.
- Reused the existing install-channel detection and update command
runner that the TUI already uses for update prompts.
- Exposed the update-action lookup from `codex-tui` so the CLI can
invoke the same behavior.
- Added CLI coverage to ensure `codex update` is parsed as a subcommand
instead of becoming an interactive prompt.
## Verification
- `cargo test -p codex-cli`
- `cargo test -p codex-tui update_action::tests`
willwang-openai