style(insights): tighten mood chart heights and unify the overview rhythm

The mood line chart plots a 1-5 score band; the 240/280 px full-mode height
left a dead strip below the line on the mood subpage. Trim the default to
200/220 px (a per-mount --chart-height override still wins) and lower the
mood-correlation scatter height so the cards fit their content without the
empty gap.

The overview used space-y-8 between top-level blocks while the vitals wrap used
space-y-6, reading as two tiers. Unify to space-y-6 for one consistent vertical
rhythm down the page, in line with the denser-Insights direction.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/app/insights/page.tsx

@@ -305,7 +305,12 @@ export default function InsightsPage() {
   // removed in v1.12.4 — the tab-strip regenerate button is the single
   // affordance. The generic disclaimer lives once in the layout-shell footer.
   return (
-    <div className="space-y-8">
+    // v1.12.7 (L3) — one consistent vertical rhythm down the overview. The
+    // page used `space-y-8` (32 px) between top-level blocks while the vitals
+    // wrap used `space-y-6` (24 px), so the overview read as two tiers. Unify
+    // to `space-y-6` — it matches the vitals wrap and tightens the overview in
+    // line with the "Insights gives away too much space" direction.
+    <div className="space-y-6">
       <HeroStrip
         briefing={briefingPayload}
         updatedAt={heroStripUpdatedAt}