fix(oracle-r8): approvals read-only by default + buyer-safe llm hint

Two Oracle round-8 blockers:

1. Approvals action buttons stayed enabled even though the actual
   runtime engine submit path is known-500. The runtime-values GET
   probe proved EA2 reachability, not action-path readiness — Oracle
   rejected 'fail-once-then-disable' for a primary buyer CTA.

   Now: actionsEnabled starts FALSE. Approvals shows a 'Read-only
   view' note with an explicit 'Enable live actions' checkbox. Action
   buttons stay disabled until the operator opts in. If a click then
   500s, actionsEnabled flips back off and the toast says 'Live actions
   have been turned back off.' No first-click-into-error.

2. Agent OFF hint exposed raw env var names OPENAI_API_KEY /
   ANTHROPIC_API_KEY. Replaced with buyer-safe 'Natural language
   replies are not enabled in this environment.'

Also removed the runtimeHealth probe entirely (Oracle's nit: the
probe's semantics were misleading — it only proved reachability,
not action-path readiness).

src/index.css

@@ -2141,3 +2141,11 @@ select.studio-input { background: var(--bp-paper); }
 .agent-llm-off { color: var(--bp-muted); }
 .agent-llm-unknown { color: var(--bp-muted); }
 .agent-llm-hint { font-size: 11px; color: var(--bp-muted); line-height: 1.4; }
+
+.approvals-actions-toggle {
+  display: inline-flex; align-items: center; gap: 6px;
+  margin-left: 10px;
+  font-family: var(--bp-mono); font-size: 11px;
+  color: var(--bp-navy); cursor: pointer;
+}
+.approvals-actions-toggle input { cursor: pointer; }