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.

internal/verifier/policy_parity_test.go

@@ -184,12 +184,15 @@ func modelOfferedActions(t *testing.T, verb string) map[string]Action {
 
 // actionIdentity keys an action by everything except the values the policy owns
 // rather than the candidate set: the typed text, which the seeded arm draws from
-// the edge-case corpus and the model writes itself, and a swipe's drag distance,
-// which the seeded arm draws and the enumeration lists at a nominal length.
+// the edge-case corpus and the model writes itself, a swipe's drag distance,
+// which the seeded arm draws and the enumeration lists at a nominal length, and
+// the source, which names who produced an action rather than what it does (the
+// enumeration names nobody, because the model has not chosen yet).
 // Comparing those would compare policies instead of action spaces. A swipe's
 // direction is NOT policy-owned, so it survives as the sign of the drag.
 func actionIdentity(action Action) string {
 	action.Text = ""
+	action.Source = ""
 	if action.Kind == ActionKindSwipe {
 		action.ToX = sign(action.ToX - action.FromX)
 		action.ToY = sign(action.ToY - action.FromY)