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/actions_act.go

@@ -57,7 +57,7 @@ func (h *reactiveHandler) actionAct(ctx context.Context, dec router.Decision) st
 			// help: everything that proposed this act — the STT, the router,
 			// the fuzzy allowlist match — is a guess, and a spoken "да" checks
 			// none of it. She names the gap instead.
-			return "это я из голоса не выполню — после него ничего не вернуть. запусти сам, если правда надо."
+			return phraser.A(phraser.ActNeedsAuthedSurface, nil)
 		case errors.Is(err, tool.ErrNotEnabled):
 			return h.proposeGap(ctx, dec)
 		case errors.Is(err, tool.ErrNotConnected), errors.Is(err, mcp.ErrNotConnected), errors.Is(err, mcp.ErrNoServer):