Changes AggregateBootstrap

Retire the aggregate bootstrap

After the aggregate workflow landed in PR #49, later PRs still scheduled its one-time pull_request preview. GitHub skipped that job with the unevaluated name expression instead of Inactive aggregate bootstrap, so the trusted aggregate rejected it as an unexpected skipped check and workflow.

Remove the obsolete preview trigger and give the aggregate its stable CI Agg name. Normal PR aggregation continues through pull_request_target, executing the trusted base reporter with read-only permissions and no PR code checkout. Merge-group aggregation and every component validation workflow remain active. No expected checks or failure criteria are weakened.

The failure was observed in PR #50 CI. Remote CI verifies the repaired event inventory and workflow policies; no local tests run. See merge queue operations.