fix(map): the popup never took the dark theme

leaflet.css paints `background: white; color: #333` on the popup card and its
tip. LeafletMapInner binds themed content into it — the school name and the
headline figure are var(--text-primary) — so in dark mode #E9EEF0 landed on
#FFFFFF at 1.17:1. The two things the popup exists to say were the two least
readable things on the page.

Every other foreground in that popup failed too, from the same cause: the
muted phase line at 2.90:1, the vs-national delta at 1.94:1, the Ofsted badge
at 1.74:1. Moving the surface onto --bg-card fixes all of them at once —
13.52, 5.45, 8.14 and 9.11:1 respectively. In light mode --bg-card is #FFFFFF,
so the popup renders exactly as it did.

globals.css already pulls the rest of Leaflet's chrome onto the tokens, and
says why: "this matters most in dark mode, where Leaflet's white attribution
bar would otherwise sit on a near-black page." The popup was simply missed.

The View Details button needed its own fix. It pairs background:var(--status-
above) with a literal white label, which theming the card does not reach:
--status-above is #36743F in light but #7FCB8A in dark, taking the label from
5.63:1 to 1.94:1. --text-inverse is the token for ink on a saturated fill, and
the popup's own Ofsted badge already uses it.

darkThemeSafety already guards this defect class, but only inside .module.css.
Neither half of this one lives there — the surface is a third party's, the
text is inline in a TSX template — so it scanned clean throughout. Two rules
added for the layer it could not see. Fixing the grouped-selector blind spot
in its rules() helper was needed to write them: taking only a selector's last
line discarded every selector in a grouped rule but the final one, which makes
a safety guard fail open.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FuPUioHpxtaiDNagQvjxyM

nextjs-app/app/globals.css

@@ -588,6 +588,35 @@ html .leaflet-bar a:hover {
     color: var(--text-primary);
 }
 
+/*
+ * The popup, which leaflet.css paints `background: white; color: #333` on both
+ * the card and its tip. The content LeafletMapInner binds into it is themed —
+ * the school name and the headline figure are `var(--text-primary)` — so in
+ * dark mode that was #E9EEF0 on #FFFFFF, a contrast ratio of 1.17:1. The name
+ * and the number were the two least readable things on the page.
+ *
+ * Moving the surface onto --bg-card fixes every foreground at once rather than
+ * one at a time: the muted phase line goes 2.90:1 -> 5.45:1, the vs-national
+ * delta 1.94:1 -> 8.14:1, the Ofsted badge 1.74:1 -> 9.11:1. In light mode
+ * --bg-card is #FFFFFF, so the popup looks as it always did.
+ */
+html .leaflet-popup-content-wrapper,
+html .leaflet-popup-tip {
+    background: var(--bg-card);
+    color: var(--text-primary);
+}
+
+/* Leaflet's own selector is `.leaflet-container a.leaflet-popup-close-button`
+   at 0,2,1 — an `html` prefix alone would lose to it. */
+html .leaflet-container a.leaflet-popup-close-button {
+    color: var(--text-muted);
+}
+
+html .leaflet-container a.leaflet-popup-close-button:hover,
+html .leaflet-container a.leaflet-popup-close-button:focus {
+    color: var(--text-primary);
+}
+
 /* Main content column */
 .main {
     max-width: 1400px;