execution/execmodule: audit published-SD readers (Events.LatestSD, bg-commit) for shared-cache coherence

#22198 detached the SDs that create their *own* read snapshot outside the exec-module semaphore (payload builds, RPC-side `NewSharedDomains` sites) from the shared commitment BranchCache. A different reader class remains unaudited: goroutines reading *through the published canonical SD* while head progresses — `Events.LatestSD` consumers and the bg-commit configs. Their reads run without the semaphore, and read-fills they trigger (BranchCache, and the account/storage StateCache) land in shared caches from positions that may not be synchronized with the FCU flush/refresh cycle.

Audit whether those read-fills can land stale under the last-Put-wins semantics (the #22152 mechanism), and guard or detach as needed.