style(node): tighten the comments and probe assertion from the QA pass

Two follow-ups on the preceding fixes, no behaviour change:

- The sweep comment in inbound_node.go had grown to a contiguous six-line
  block, over the two-line maximum. The prefix rationale it carried is
  already stated by nodeSelectedTagSet itself and by 6f40a51d's message.
- The probe cap test asserted only that an error came back, which cannot
  tell a size rejection from a transport failure or a success=false
  envelope. It now pins LastError to the decode rejection.

Both remain red-first: neutralizing maxProbeBodyBytes still fails the probe
test on the new assertion.

internal/web/service/inbound_node.go

@@ -173,8 +173,6 @@ func (s *InboundService) ReconcileNode(ctx context.Context, rt *runtime.Remote,
 	// rest were never imported, so their absence from the local DB must not
 	// delete them from the node. Only a selected tag missing locally (the
 	// panel deleted it while the node was unreachable) may be swept.
-	// The node reports a panel-created inbound with its n<id>- prefix stripped,
-	// so the selected set must carry both forms or the sweep never matches.
 	selected := nodeSelectedTagSet(n)
 	for _, tag := range remoteTags {
 		if _, want := desiredTags[tag]; want {