tool, mavend: Hexis owns the tier of a Hexis capability (V-523)

read_only was the whole decision on the Hexis act path, which flattened three
answers into two. A capability that wipes the thing it names got the same
single spoken "да" as one that restarts a service, and requires_confirmation —
which the Hexis contract calls server-derived and never settable by a caller —
was read by nobody. docs/ecosystem.md §17.3 says confirmation follows risk.

RiskOfCapability reads Hexis's risk, read_only and requires_confirmation and
returns one of the three tiers internal/tool already had. It takes plain values
rather than a Capability, so internal/tool keeps no dependency on the Hexis
client. RiskOf keeps deriving, because a shell row the owner ticked on /tools
has no upstream to ask.

Every disagreement between the three fields goes up, never down: safe and
mutating is a contradiction and takes the confirm, an unrecognised tier takes
the confirm, and requires_confirmation may only raise. Same default as an
unrecognised dispatch shape — argue your way down, never up.

The irreversible refusal was a Go literal in two places and is now one deck
entry, act_needs_authed_surface. It lost four words to the persona ceiling.

cmd/mavend/ecosystem_test.go

@@ -253,3 +253,62 @@ func actRan(reply string) bool {
 
 // muzickIndexer — the display name every ecosystem fixture resolves to.
 const muzickIndexer = "Muzick indexer"
+
+// read_only used to be the whole decision on this path, which meant a
+// capability that destroys what it names got the same single spoken "да" as one
+// that restarts a service. Hexis declares the tier and the voice path is not an
+// authorised surface for the top one (Vikunja #523).
+func TestHexisIrreversibleCapabilityIsNotRunFromVoice(t *testing.T) {
+	ctx := context.Background()
+	resolved := `{"status":"resolved","entity":{"id":"ent_muzick","display_name":"Muzick indexer","type":"service"}}`
+	caps := `[{"id":"cap_wipe","name":"restart","read_only":false,"risk":"irreversible","requires_confirmation":true}]`
+	h, executed := newHexisTestHandler(t, resolved, caps)
+
+	reply := h.handleHexisAct(ctx, actDec("muzick indexer"))
+	if *executed {
+		t.Fatal("an irreversible capability ran from the voice path")
+	}
+	if h.pendingHexis != nil {
+		t.Fatal("an irreversible capability parked a confirm; a spoken да is not enough authority")
+	}
+	if !strings.Contains(reply, "не вернуть") {
+		t.Errorf("reply = %q; want it to name why she will not run it", reply)
+	}
+}
+
+// The other half: Hexis calling a capability safe is enough to run it, even
+// though read_only is the field that used to decide. Nothing here re-derives.
+func TestHexisSafeCapabilityRunsOnItsDeclaredTier(t *testing.T) {
+	ctx := context.Background()
+	resolved := `{"status":"resolved","entity":{"id":"ent_muzick","display_name":"Muzick indexer","type":"service"}}`
+	caps := `[{"id":"cap_status","name":"restart","read_only":true,"risk":"safe"}]`
+	h, executed := newHexisTestHandler(t, resolved, caps)
+
+	reply := h.handleHexisAct(ctx, actDec("muzick indexer"))
+	if !*executed {
+		t.Fatal("a capability Hexis calls safe should run")
+	}
+	if !actRan(reply) {
+		t.Fatalf("unexpected reply %q", reply)
+	}
+}
+
+// A mutating capability with no declared tier keeps the confirm turn it has
+// always had, so the split does not quietly loosen an existing box.
+func TestHexisUndeclaredTierStillConfirms(t *testing.T) {
+	ctx := context.Background()
+	resolved := `{"status":"resolved","entity":{"id":"ent_muzick","display_name":"Muzick indexer","type":"service"}}`
+	caps := `[{"id":"cap_restart","name":"restart","read_only":false}]`
+	h, executed := newHexisTestHandler(t, resolved, caps)
+
+	reply := h.handleHexisAct(ctx, actDec("muzick indexer"))
+	if *executed {
+		t.Fatal("a mutating capability ran without a confirm")
+	}
+	if h.pendingHexis == nil {
+		t.Fatal("a mutating capability did not park a confirm")
+	}
+	if !strings.Contains(reply, "да или нет") {
+		t.Errorf("reply = %q; want the confirm question", reply)
+	}
+}