Tree: clicking ×N flies to the person's other copy (not just flashes)

On a large tree the duplicate's other copy is usually off-screen, so flashing
in place wasn't enough. Clicking the ×N badge now pans/zooms the view to center
the other copy and flashes it on arrival; clicking again cycles through the
remaining copies (for a person drawn 3+ times).

Uses family-chart's exported handlers: cardToMiddle centers a datum (read from
the target card_cont's bound x/y, falling back to its transform attr), keeping
the current zoom level via getCurrentZoom. Verified against the lib: the svg's
parent (f3Canvas) holds the zoom object, and cards are positioned by datum x/y —
same coordinate space cardToMiddle expects. Falls back to an in-place flash if
the zoom object isn't ready. Frontend only; supersedes the flash-only behavior.

Signed-off-by: Justin Paul <justin@jpaul.me>

frontend/app/trees/[id]/tree/page.tsx

@@ -36,6 +36,12 @@ export default function TreePage() {
   const containerRef = useRef<HTMLDivElement>(null);
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   const chartRef = useRef<any>(null);
+  // family-chart's pan/zoom helpers (cardToMiddle, getCurrentZoom), captured at
+  // render — used to fly to a duplicate's other copy.
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  const handlersRef = useRef<any>(null);
+  // Per-person cursor so repeated clicks on a ×N badge cycle through the copies.
+  const dupCycle = useRef<Map<string, number>>(new Map());
   const [query, setQuery] = useState("");
 
   const [people, setPeople] = useState<Person[]>([]);
@@ -189,6 +195,7 @@ export default function TreePage() {
         };
       });
       const f3 = await import("family-chart");
+      handlersRef.current = f3.handlers;
       if (cancelled || !containerRef.current) return;
       try {
         containerRef.current.innerHTML = "";
@@ -252,31 +259,76 @@ export default function TreePage() {
     [mode],
   );
 
-  // Click the "×N" duplicate badge on a card to flash every copy of that person
+  // Click the "×N" duplicate badge to FLY to the person's other copy in the
-  // in the current view. They're the same record drawn in two places (a shared
+  // view (cycling through them on repeat clicks) and flash it on arrival. The
-  // ancestor, or an intermarriage). Delegated on the container so it survives
+  // same record is drawn in two places (a shared ancestor, or an intermarriage),
-  // chart rebuilds; capture-phase + stopPropagation so it doesn't also recenter.
+  // and on a big tree the other copy is usually off-screen. Delegated on the
+  // container so it survives chart rebuilds; capture-phase + stopPropagation so a
+  // badge click flies instead of recentering.
   useEffect(() => {
     const el = containerRef.current;
     if (!el) return;
-    type Bound = Element & { __data__?: { data?: { id?: string } } };
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    const idOf = (node: Element | null) => (node as Bound | null)?.__data__?.data?.id;
+    const data = (n: Element | null) => (n as any)?.__data__;
+    const idOf = (n: Element | null) => data(n)?.data?.id as string | undefined;
+    const xyOf = (cont: Element): { x: number; y: number } | null => {
+      const d = data(cont);
+      if (d && typeof d.x === "number" && typeof d.y === "number") return { x: d.x, y: d.y };
+      const m = /translate\(\s*([-\d.]+)[ ,]+([-\d.]+)/.exec(cont.getAttribute("transform") ?? "");
+      return m ? { x: parseFloat(m[1]), y: parseFloat(m[2]) } : null;
+    };
+    const flash = (cont: Element | null) => {
+      const card = cont?.querySelector(".card") as HTMLElement | null;
+      if (!card) return;
+      card.classList.remove("f3-card-flash");
+      void card.offsetWidth; // restart the animation on repeat clicks
+      card.classList.add("f3-card-flash");
+      window.setTimeout(() => card.classList.remove("f3-card-flash"), 1900);
+    };
+
     function onClick(e: MouseEvent) {
       const tag = (e.target as HTMLElement).closest?.(".f3-card-duplicate-tag");
       if (!tag) return;
       e.preventDefault();
       e.stopPropagation();
-      const id = idOf(tag.closest(".card_cont"));
+      const clicked = tag.closest(".card_cont");
+      const id = idOf(clicked);
       if (!id) return;
-      el!.querySelectorAll(".card_cont").forEach((cont) => {
+      const copies = Array.from(el!.querySelectorAll(".card_cont")).filter((c) => idOf(c) === id);
-        if (idOf(cont) !== id) return;
+      if (copies.length < 2) {
-        const card = cont.querySelector(".card") as HTMLElement | null;
+        flash(clicked);
-        if (!card) return;
+        return;
-        card.classList.remove("f3-card-flash");
+      }
-        void card.offsetWidth; // restart the animation on repeat clicks
+      // Advance from wherever we last landed (or the clicked card), skipping the
-        card.classList.add("f3-card-flash");
+      // clicked copy, so each click moves to the next other location.
-        window.setTimeout(() => card.classList.remove("f3-card-flash"), 1900);
+      const start = dupCycle.current.get(id) ?? copies.indexOf(clicked as Element);
-      });
+      let next = (start + 1) % copies.length;
+      if (copies[next] === clicked) next = (next + 1) % copies.length;
+      dupCycle.current.set(id, next);
+      const target = copies[next];
+
+      const handlers = handlersRef.current;
+      const svg = el!.querySelector("svg.main_svg") as SVGSVGElement | null;
+      const xy = xyOf(target);
+      let flew = false;
+      if (handlers?.cardToMiddle && svg && xy) {
+        try {
+          const rect = svg.getBoundingClientRect();
+          const scale = handlers.getCurrentZoom ? handlers.getCurrentZoom(svg).k : 1;
+          handlers.cardToMiddle({
+            datum: xy,
+            svg,
+            svg_dim: { width: rect.width, height: rect.height },
+            scale,
+            transition_time: 750,
+          });
+          flew = true;
+        } catch {
+          /* zoom not ready — fall back to flashing in place */
+        }
+      }
+      // Flash on arrival (after the fly), or immediately if we couldn't fly.
+      window.setTimeout(() => flash(target), flew ? 900 : 0);
     }
     el.addEventListener("click", onClick, true);
     return () => el.removeEventListener("click", onClick, true);
@@ -453,7 +505,7 @@ export default function TreePage() {
                   person appears N times in the current view. The same record is drawn in
                   two places because they connect through more than one line (a shared
                   ancestor, or an intermarriage).{" "}
-                  <span className="text-[var(--muted)]">Click the ×N to flash the other copies.</span>
+                  <span className="text-[var(--muted)]">Click the ×N to fly to the other copies (click again to cycle).</span>
                 </li>
                 <li className="flex flex-wrap items-center gap-x-2 gap-y-1">
                   <span className="inline-flex items-center gap-1">