🐛 Guard renders against heavy graphs; add ?safe escape hatch

A heavy file could freeze the tab on load-and-render despite the animation gate: the render guard counted nodes only, and the edge-bundling plugin is iteration-heavy in edges. Guard now also trips on edges (8000), edge bundling only activates at <= 300 edges, and /dbg/graph?safe disables auto-render entirely (counts + "Render anyway"), so a page that hung can always be re-entered with the session intact.

Signed-off-by: Álvaro Tejero Cantero <alvorithm@teje.ro>

backend/resources/app/templates/graph-console.tmpl

@@ -570,9 +570,16 @@ Graph Console
   // Legend glyph characters mirroring the G6 node types above.
   const GLYPH_CHARS = { diamond: "◆", rect: "■", hexagon: "⬢",
                         circle: "●", triangle: "▲", star: "★" };
-  // Above this many nodes the view is not rendered automatically; the
+  // Above this many nodes/edges the view is not rendered automatically;
-  // "Render anyway" button forces it (~1.5 s per 2k nodes, measured).
+  // the "Render anyway" button forces it (~1.5 s per 2k nodes, measured;
+  // edges gate the guard too since plugin/combo cost scales with them).
+  // Escape hatch: /dbg/graph?safe disables auto-render entirely, so a
+  // page that hung on render can always be re-entered.
   const RENDER_GUARD_NODES = 4000;
+  const RENDER_GUARD_EDGES = 8000;
+  // Edge bundling is iteration-heavy in the number of edges — a
+  // page-freezing cost at scale; bundle only small graphs.
+  const BUNDLE_MAX_EDGES = 300;
   // G6's entrance/update animation is nice didactics on small graphs but
   // the performance killer at scale (>2 min at 1700 nodes vs ~1.5 s off);
   // keep it only below this node count.
@@ -910,7 +917,7 @@ Graph Console
         // empty canvas clears. Runs alongside the node:click inspector.
         { type: "click-select", degree: 1,
           state: "selected", neighborState: "active", unselectedState: "inactive" }],
-      plugins: [{key: "edge-bundling", type: "edge-bundling"},{
+      plugins: [{
         key: "toolbar",
         type: "toolbar",
         position: "top-left",
@@ -936,6 +943,9 @@ Graph Console
       }]
     };
     if (layoutCfg) opts.layout = layoutCfg;
+    if (g6data.edges.length <= BUNDLE_MAX_EDGES) {
+      opts.plugins.unshift({ key: "edge-bundling", type: "edge-bundling" });
+    }
     g6graph = new G6.Graph(opts);
     // Re-attached on every instance creation (layout/animation switches
     // destroy and recreate the graph).
@@ -1070,9 +1080,14 @@ Graph Console
       ? " — query filter: " + data.nodes.length + " of "
         + lastGraphData.nodes.length + " nodes"
       : "";
-    if (shown.nodes.length > RENDER_GUARD_NODES && !renderForced) {
+    const safeMode = new URLSearchParams(location.search).has("safe");
+    if ((safeMode
+         || shown.nodes.length > RENDER_GUARD_NODES
+         || shown.edges.length > RENDER_GUARD_EDGES) && !renderForced) {
       graphViewStatus.textContent =
-        graphStatusText(data) + filterNote + " — too large to render automatically";
+        graphStatusText(data) + filterNote
+        + (safeMode ? " — safe mode (?safe): auto-render off"
+                    : " — too large to render automatically");
       if (anywayBtn) anywayBtn.style.display = "inline";
       return;
     }