Public tree view: full-width canvas like the member view

The public layout forced max-w-5xl on every /p page, so the tree chart was
cramped. Mirror the member shell: the public layout now drops the max-width for
the tree page (/p/<id>) only, giving the chart the full canvas (74vh to match
the member view), while the page keeps its heading and people list in a
centered max-w-5xl column. Person detail (/p/<id>/persons/<pid>) and /explore
stay narrow.

tsc clean; next build passes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>

frontend/components/public-tree-chart.tsx

@@ -160,7 +160,7 @@ export function PublicTreeChart({
       <div
         ref={containerRef}
         className="f3 rounded-xl border border-[var(--border)]"
-        style={{ width: "100%", height: "70vh", background: "var(--surface)" }}
+        style={{ width: "100%", height: "74vh", background: "var(--surface)" }}
       />
       <div className="flex flex-wrap items-center justify-between gap-2">
         <p className="text-sm text-[var(--muted)]">