Erase terminal signings in bulk

Purges the client's terminal signing records and any order-owned uploads. Pre-existing vault documents used through MCP are preserved. In-flight signings are left untouched; erase one directly if cancellation is intended. Processes at most limit resources across signings and headless signatures (default 20, maximum 100). After ten seconds of processing, finishes the current resource and returns a continuation; a single storage operation still depends on its transport timeout. Follow nextCursor while hasMore is true. The cursor binds the client and the initial cutoff; before may be omitted on continuation, or must match the first request. Failed resources are listed and skipped by the cursor so they cannot block later pages. After finishing the traversal, retry failures with a new request without a cursor. hasMore: false ends this traversal, not a claim that failed resources or later-terminal records were erased.