4ef6ce5e — fetch ONE sprint item's live row, scoped to project_id.

Added alongside claim_verification_mode: this is what meridian.claim_verify.fetch_sprint_item_live calls from the PostToolUse hook to re-check a claim_sprint_item/complete_sprint_item call's real, live outcome — deliberately a plain DB read straight from the server, never anything the calling session's own narration could influence. 404 when the item doesn't exist or belongs to a different project (same not-found shape either way — no project-existence oracle leaked through this endpoint).