Preserve update-time config state by snapshotting before repair/restart writes, keeping plugin install records available for migration, and blocking unsafe update-time config size drops.
Also documents the Codex reserved SDK subpaths needed by the plugin contract guardrail.
Fixes#80077.
Thanks @Jerry-Xin and @vincentkoc.
Co-authored-by: Jerry-Xin <3401616+Jerry-Xin@users.noreply.github.com>
Co-authored-by: Vincent Koc <25068+vincentkoc@users.noreply.github.com>