fix(admin): KI-184 — Refresh forces fresh probe + tier banner

User report: "refresh doesn't work."

Root cause: KI-164's admin-strip removed the "Force fresh probe (slow)"
button. The remaining Refresh button only called fetchLlmHealth() which
re-fetches the cached probe state from /api/admin/llm-health. The
backend's probe loop runs every 5 min independently. So clicking Refresh
on a 2-minute-old snapshot just re-showed the same 2-minute-old data.

Fix: Refresh now POSTs /api/admin/probe first (forces fresh probe), then
re-fetches state, then re-renders. Same as the legacy "Force fresh
probe" button used to do. Button now reads "Probing…" during the call
so the user knows it's actually doing work.

Plus: added a tier banner ABOVE the What's Live table that explains
the 3-tier chain: Gemini Tier 0 (primary) → NIM Tier 1 (what's shown
below) → OpenRouter Tier 2 → NIM Nemotron-49B last resort. This
prevents confusion when the user sees nemotron showing as "primary"
in the NIM table even though Gemini is actually serving traffic
(per KI-179 + ADR-040).

Verification: node --check on inline script — clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/public/admin/llm-control.html

@@ -675,6 +675,19 @@
             <button id="btn-refresh-llm-health">Refresh</button>
           </div>
         </div>
+        <!-- KI-184 (2026-05-15) — Tier banner so the table below isn't
+             confused with the actual primary serving traffic. Real-world
+             call order: Tier 0 Google Gemini → Tier 1 NIM (shown below) →
+             Tier 2 OpenRouter free pool → NIM nemotron-49b last resort. -->
+        <div style="margin-bottom: 14px; padding: 10px 14px; border: 1px solid var(--border); border-radius: 8px; background: #0b0d12; font-size: 12px; line-height: 1.5;">
+          <strong style="color: var(--text);">3-tier brain chain (KI-179 + ADR-040):</strong>
+          <span class="muted">
+            Tier 0 — <strong>Google Gemini 2.5 Flash / Flash Lite</strong> (PRIMARY, free 1500/day)
+            &nbsp;·&nbsp; Tier 1 — NIM (shown below)
+            &nbsp;·&nbsp; Tier 2 — OpenRouter free pool
+            &nbsp;·&nbsp; Last resort — NIM Nemotron-49B
+          </span>
+        </div>
         <div id="llm-health-chains" class="llm-simple-tables"></div>
       </div>
     </section>
@@ -2404,14 +2417,21 @@
         // handlers are gone.
 
         // KI-086 — manual refresh for the LLM Health & Credits card.
+        // KI-184 (2026-05-15) — Refresh now forces a fresh probe BEFORE
+        // fetching state. Previously this only re-fetched the cached probe
+        // state from /api/admin/llm-health, which is refreshed by a 5-min
+        // background loop. User clicked Refresh expecting current state but
+        // got cached state. Now: POST /api/admin/probe → then re-fetch.
         var llmHealthBtn = $('btn-refresh-llm-health');
         if (llmHealthBtn) {
           llmHealthBtn.onclick = function () {
             var btn = this;
             btn.disabled = true;
-            btn.textContent = 'Refreshing…';
-            fetchLlmHealth()
-              .then(function () { renderLlmHealth(); toast('LLM health refreshed', 'success'); })
+            btn.textContent = 'Probing…';
+            apiPost('/api/admin/probe', null)
+              .catch(function () { /* tolerate probe failure; still re-fetch cached state */ })
+              .then(function () { return fetchLlmHealth(); })
+              .then(function () { renderLlmHealth(); toast('LLM health refreshed (fresh probe)', 'success'); })
               .catch(handleFetchErr)
               .then(function () { btn.disabled = false; btn.textContent = 'Refresh'; });
           };