fix(visualize): mind-map fills & centres the viewport (was cramped in a corner)

- centre the tree in the viewport (vertical centring when it fits; margin
  auto for horizontal) instead of pinning it to the top-left corner
- expand all documents by default so the tree is full and reads as a rich
  mind-map rather than a few lonely collapsed nodes
- click +/- still folds/unfolds any branch

Author: KylinMountain

openkb/templates/graph.html

@@ -380,7 +380,8 @@
       + (hasKids ? `<span class="mm-caret" data-tog="${esc(it.id)}">${mmCollapsed.has(it.id) ? "+" + (kidsOf[it.id] || []).length : "−"}</span>` : ``)
       + `</div>`;
   });
-  mmEl.innerHTML = `<div class="mm-canvas" style="width:${Wpx}px;height:${Hpx}px">${svg}${html}</div>`;
+  const offY = Math.max(0, (mmEl.clientHeight - Hpx) / 2);   // centre vertically when it fits; else scroll
+  mmEl.innerHTML = `<div class="mm-canvas" style="width:${Wpx}px;height:${Hpx}px;margin:${offY}px auto 0">${svg}${html}</div>`;
   mmEl.querySelectorAll("[data-tog]").forEach(el => el.onclick = e => {
     e.stopPropagation(); const id = el.dataset.tog;
     if(mmCollapsed.has(id)) mmCollapsed.delete(id); else mmCollapsed.add(id);
@@ -882,7 +883,7 @@
 document.getElementById("reset").addEventListener("click", () => {
   hover = null; closePanel();
   if(mode === "mindmap"){
-    mmQuery = ""; search.value = ""; mmCollapsed.clear(); collapseDocs(); buildMindmap(); mmEl.scrollTop = 0; mmEl.scrollLeft = 0;
+    mmQuery = ""; search.value = ""; mmCollapsed.clear(); buildMindmap(); mmEl.scrollTop = 0; mmEl.scrollLeft = 0;
   } else if(mode === "radial"){
     spread = DEFAULT_SPREAD; spreadEl.value = String(DEFAULT_SPREAD); panX = 0; panY = 0;
     scale = DEF_SCALE; yaw = 0; pitch = 0; layoutRadial();
@@ -896,9 +897,8 @@
 });
 
 /* ===================== boot ===================== */
-function collapseDocs(){ nodes.forEach(n => { if(n.id.startsWith("summaries/")) mmCollapsed.add(n.id); }); }  // start compact: docs folded
 window.addEventListener("resize", () => { size(); autoFit = true; if(mode === "mindmap") buildMindmap(); });
-size(); seed(); collapseDocs();
+size(); seed();
 setMode("graph");        // open on the 3D nebula
 requestAnimationFrame(frame);
 </script>