hub: fix .data-table btn contrast + customer page hash tabs (v0.47.0 part 1-2)

- style.css: .data-table td a -> :not(.btn) so <a class=btn> keeps the .btn
  palette (View/Download buttons were blue-on-blue invisible)
- customer_unified.html: 8 client-side hash tabs (#tab=...) + sticky summary
  strip; all sections preserved in DOM, hiding is a JS-added body class only
  (no-JS = everything visible); Events tab gets a red error-count badge
- new render tests: TestTemplates_CustomerTabs (+_NoReports)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Vvz1NCu22p8dGkRCpeX9re

hub/internal/web/templates/style.css

@@ -864,12 +864,14 @@ code {
     font-family: var(--font-data);
     font-size: 0.875rem;
 }
-.data-table td a {
+/* Plain links only — :not(.btn) keeps <a class="btn"> buttons on the .btn palette
+   (blue-bright link text on a blue-bright button background is invisible). */
+.data-table td a:not(.btn) {
     color: var(--blue-bright);
     text-decoration: none;
     font-family: var(--font-sans, sans-serif);
 }
-.data-table td a:hover { text-decoration: underline; }
+.data-table td a:not(.btn):hover { text-decoration: underline; }
 .data-table th a {
     color: var(--text-2);
     text-decoration: none;
@@ -908,6 +910,65 @@ header h1 span { color: var(--blue-bright); }
 
 :focus-visible { outline: 2px solid var(--blue-bright); outline-offset: 1px; }
 
+/* ── Customer page tabs (v0.47.0) ──────────────────────────────────────────
+   Hash-based client-side tabs. Graceful degradation is load-bearing: panels
+   are hidden ONLY under body.js-tabs (added by JS on DOMContentLoaded) — with
+   JS off every panel stays visible and the page reads top-to-bottom. */
+.summary-strip {
+    position: sticky;
+    top: 0;
+    z-index: 40;
+    display: flex;
+    align-items: center;
+    gap: 1rem;
+    flex-wrap: wrap;
+    padding: 0.5rem 0.75rem;
+    margin: 0.75rem 0 0;
+    background: var(--bg-0);
+    border: 1px solid var(--line);
+    border-radius: var(--radius);
+    font-size: 0.85rem;
+}
+.summary-strip .strip-name { font-weight: 600; color: var(--text-1); }
+.summary-strip .strip-item { color: var(--text-2); white-space: nowrap; }
+.summary-strip .strip-item code { font-size: 0.85em; }
+
+.tab-nav {
+    display: flex;
+    gap: 0.25rem;
+    margin: 0.75rem 0 1rem;
+    border-bottom: 1px solid var(--line);
+    overflow-x: auto;
+    white-space: nowrap;
+}
+.tab-nav a {
+    color: var(--text-2);
+    text-decoration: none;
+    font-size: 0.9rem;
+    padding: 0.45rem 0.75rem;
+    border-bottom: 2px solid transparent;
+    flex-shrink: 0;
+}
+.tab-nav a:hover { color: var(--text-1); }
+.tab-nav a.active {
+    color: var(--blue-bright);
+    border-bottom-color: var(--blue-bright);
+    font-weight: 600;
+}
+.tab-badge {
+    display: inline-block;
+    min-width: 1.2em;
+    margin-left: 0.35em;
+    padding: 0 0.35em;
+    background: var(--crit);
+    color: #fff;
+    border-radius: var(--radius);
+    font-size: 0.75em;
+    font-weight: 600;
+    text-align: center;
+}
+body.js-tabs .tab-panel:not(.tab-panel-active) { display: none; }
+
 @media (prefers-reduced-motion: reduce) {
     *, *::before, *::after { animation: none !important; transition: none !important; }
 }