fix(trace): an action names the generator that produced it

The setup exclusion landed for the model arm only, because only a model
pick stamped a source. A seeded run returned setup's action through the
same entry with no marker, so its denominator still counted the login
while the model arm's did not, and the two are compared.

serializeAction names setup and seeded on the wire, so both arms are
counted by one rule. An already-recorded trace names nothing and keeps
exactly the count it was reported with; unattributed_actions counts those
steps so the old denominator cannot pass as the new one. TraceVersion is
deliberately unbumped: oracle-reduction refuses a differing version, and
a bump would make all 169 recorded runs unreplayable.

cmd/internal-tools/analyze/analysis.go

@@ -225,9 +225,10 @@ func summarize(current arm) armSummary {
 		}
 		summary.Usable++
 		summary.TotalSteps += item.Steps
-		// Steps and actions differ by the steps that chose no action and the
-		// steps whose action was never dispatched. Only dispatched actions
-		// exercised the app, so only they belong in a per-action rate.
+		// Steps and actions differ by the steps that chose no action, the steps
+		// whose action was never dispatched, and the steps the spec's setup
+		// drove into position. Only what the action generator dispatched
+		// explored the app, so only that belongs in a per-action rate.
 		summary.TotalActions += item.Actions
 		summary.TotalRunHours += float64(item.MonotonicMillis) / float64(time.Hour/time.Millisecond)
 		if item.ClampedToBudget {