[codex] Cache remote plugin catalog for suggestions

[xl-openai]

Summary

• cache the global remote plugin catalog when remote plugin listing runs and warm it during startup
• use the cached remote catalog in plugin install recommendations with canonical plugin@openai-curated-remote ids
• reuse the session PluginsManager for plugin recommendations so remote cache state is visible on the recommend path
• skip core installed-state verification for remote plugin install suggestions while leaving local plugin and connector verification unchanged

Testing

• just fmt
• git diff --check
• cargo test -p codex-core list_tool_suggest_discoverable_plugins_includes_cached_remote_global_plugins
• cargo test -p codex-core remote_plugin_install_suggestions_skip_core_installed_verification
• cargo test -p codex-app-server plugin_list_includes_remote_marketplaces_when_remote_plugin_enabled

Earlier focused checks during the same branch: codex-tools TUI filter test, request_plugin_install tests, and codex-app-server build.

[chatgpt-codex-connector]

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