Let observers' findings and a carried holder's seat events reach the bus (issue 1952)

A finding's field `token` is named like a credential, so the tool runner
refused every finding that carried it; it is `ref` now, and a finding
written under the old name is still read. A module the tool runner
carries got no grant for its own held seat's events, so the self-check
could not say `checked`; a held plain seat's events are now in the
holder's seat traffic, its membership and its runtime's grants.

Quick vs thorough: quick, these fixes for L4's take-over now; the
thorough fix (research 032 / ADR 0240's health view extension) is
decided later.

Claude-Session: https://claude.ai/code/session_01NcbgfJ9Gum47zkFKWRaovL

go/buscompose/buscompose_test.go

@@ -251,6 +251,7 @@ func TestTheCopiedComposerComposesAsTheControllers(t *testing.T) {
 			if err := json.Unmarshal(want[i].Memberships, &wasM); err != nil {
 				t.Fatal(err)
 			}
+			heldEventsBeyond(gotM, wasM)
 			if !reflect.DeepEqual(gotM, wasM) {
 				t.Errorf("the memberships differ from the controller's:\n%s", raw)
 			}
@@ -825,6 +826,37 @@ func healthChecks(t *testing.T) {
 		URL: "nats://a:4222"}); w.Valid() != nil || w.OwnSecret() != "broker-nats-tools" {
 		t.Errorf("the tools account is held in %q (%v)", w.OwnSecret(), w.Valid())
 	}
+	// Issue 1952: a module that holds a seat says its own seat's events, also when the tool runner carries it, so the
+	// self-check's `checked`, the keeper's condition events and the healers' `healer-acted` reach their hearers. Its
+	// membership lists them, the runtime is granted them; a user of the seat is not, nor a machine's event on a node seat
+	// (granted per machine, to the holder's own account only).
+	selfCheck := Declared{Module: "mesh-self-check", Holds: []Seat{{Name: "mesh-self-check", Scope: "mesh", Emits: []string{"checked"}}}}
+	for _, c := range []struct {
+		name    string
+		d       Declared
+		subject string
+		may     bool
+	}{
+		{"the self-check says checked", selfCheck, "mesh.seat.mesh-self-check.event.checked", true},
+		{"the keeper says a condition raised", Declared{Module: "mesh-conditions", Holds: []Seat{{Name: "mesh-conditions", Scope: "mesh",
+			Emits: []string{"condition-raised", "condition-cleared"}}}}, "mesh.seat.mesh-conditions.event.condition-cleared", true},
+		{"a user does not say the seat's events", Declared{Module: "mesh-delivery-view", Uses: []Seat{{Name: "mesh-self-check",
+			Scope: "mesh", Emits: []string{"checked"}}}}, "mesh.seat.mesh-self-check.event.checked", false},
+		{"the holder says no other seat's", selfCheck, "mesh.seat.mesh-conditions.event.condition-raised", false},
+		{"a machine's event on a node seat is not composed here", Declared{Module: "pause", Holds: []Seat{{Name: "node-power",
+			Scope: "node", Emits: []string{"paused.*"}}}}, "mesh.seat.node-power.event.paused.b", false},
+	} {
+		m := MembershipFor("a", c.d, Placements{})
+		listed := m.SeatTraffic != nil && slices.ContainsFunc(m.SeatTraffic.Publish, func(p string) bool { return p == c.subject })
+		perms, err := PermissionsFor(Principal{Kind: KindNodeTools, Node: "a", Carries: []Declared{c.d}})
+		if err != nil {
+			t.Fatalf("%s: %v", c.name, err)
+		}
+		if listed != c.may || MayPublish(perms, c.subject) != c.may {
+			t.Errorf("%s: the membership lists %s %v and the runtime may publish it %v, want %v", c.name, c.subject, listed,
+				MayPublish(perms, c.subject), c.may)
+		}
+	}
 	seen := map[string]bool{}
 	for _, u := range users {
 		name := u.Username()
@@ -879,3 +911,52 @@ func healthChecks(t *testing.T) {
 		}
 	}
 }
+
+// heldEventsBeyond takes out of the copy's memberships the one row they list beyond the controller's on purpose (issue
+// 1952): a held seat's own events in its holder's seat traffic, so a module the tool runner carries may say them. The
+// controller's composer is frozen; any other difference is still a fault.
+func heldEventsBeyond(got, was any) {
+	gotAll, _ := got.(map[string]any)
+	wasAll, _ := was.(map[string]any)
+	for key, m := range gotAll {
+		gm, _ := m.(map[string]any)
+		traffic, _ := gm["seat-traffic"].(map[string]any)
+		if traffic == nil {
+			continue
+		}
+		listedBefore := map[string]bool{}
+		if wm, _ := wasAll[key].(map[string]any); wm != nil {
+			if wt, _ := wm["seat-traffic"].(map[string]any); wt != nil {
+				for _, p := range asStrings(wt["publish"]) {
+					listedBefore[p] = true
+				}
+			}
+		}
+		var kept []any
+		for _, p := range asStrings(traffic["publish"]) {
+			if parts := strings.Split(p, "."); !listedBefore[p] && len(parts) == 5 && parts[0] == "mesh" && parts[1] == "seat" && parts[3] == "event" {
+				continue
+			}
+			kept = append(kept, p)
+		}
+		if kept == nil {
+			delete(traffic, "publish")
+		} else {
+			traffic["publish"] = kept
+		}
+		if len(traffic) == 0 {
+			delete(gm, "seat-traffic")
+		}
+	}
+}
+
+func asStrings(v any) []string {
+	list, _ := v.([]any)
+	out := make([]string, 0, len(list))
+	for _, x := range list {
+		if s, ok := x.(string); ok {
+			out = append(out, s)
+		}
+	}
+	return out
+}