Validation and testing improvements (bd-74, bd-77)

- Remove unreachable function DroppedEventsCount from RPC server
- Add TestMutationToExportLatency for event-driven daemon validation
- Test currently skipped pending full bd-85 implementation
- Create test coverage improvement issues (bd-114 through bd-118)
- All validation checks pass: tests, build, linting baseline

Completed: bd-74, bd-77
Amp-Thread-ID: https://ampcode.com/threads/T-24404401-6c5b-466d-9045-0da3a70cff9a
Co-authored-by: Amp <amp@ampcode.com>

internal/rpc/server_core.go

@@ -116,11 +116,6 @@ func (s *Server) MutationChan() <-chan MutationEvent {
 	return s.mutationChan
 }
 
-// DroppedEventsCount returns the number of dropped mutation events
-func (s *Server) DroppedEventsCount() int64 {
-	return s.droppedEvents.Load()
-}
-
 // ResetDroppedEventsCount resets the dropped events counter and returns the previous value
 func (s *Server) ResetDroppedEventsCount() int64 {
 	return s.droppedEvents.Swap(0)