perf(#690): avoid duplicate live index refresh

codedb_index's snapshot child notified the daemon before the MCP parent refreshed the same Explorer directly, forcing an unnecessary second tree walk and hash pass. Suppress only the child notification for the MCP-managed snapshot path while preserving standalone snapshot notifications and the parent's in-process fallback.

Co-Authored-By: Codegraff <blackfloofie@codegraff.com>