world: fade landmark orbs after 60s idle (V5)

Turns out V5 wasn't a no-op — the SSE loop stops emitting a repo:<id>
node once its topic transitions to 'published' (the query filters on
processing/reviewing/publishing), but the client engine's idle-fade
only applied to service/event tiers. Repo and loop landmarks lingered
forever on the client until page reload.

Extends the fade rule to cover repo + loop tiers, with a longer window
(60s vs 22s for service/event) so a brief SSE hiccup doesn't wipe the
whole workspace's landmarks. When a topic reaches 'published', its
`lastSeen` stops advancing on the client; ~60s later the alpha ramps
down and the node is deleted from the map.

Same rule applies to loops that get `enabled=false` after being
turned off — their landmark quietly fades out instead of persisting
until reload.

frontend/src/components/world/engine.ts

@@ -450,11 +450,23 @@ export class WorldEngine {
       n.heat = Math.max(0, n.heat - dt * 0.5);
     }
 
-    // world nodes fade out when idle (Gource file-idle), then are removed
+    // world nodes fade out when idle (Gource file-idle), then are removed.
+    // - service/event: quick fade (22s) — tool calls and one-shot events
+    //   shouldn't linger visually.
+    // - repo/loop landmarks: slow fade (60s) — a topic transitioning to
+    //   'published' stops emitting from the SSE loop; the landmark should
+    //   quietly disappear rather than hang around forever. The longer
+    //   window keeps a brief SSE hiccup from evicting the workspace.
     for (const n of arr) {
-      if (n.tier === "service" || n.tier === "event") {
+      const shortLived = n.tier === "service" || n.tier === "event";
+      const landmark = n.tier === "repo" || n.tier === "loop";
+      if (shortLived || landmark) {
         const idleAge = this.now - n.lastSeen;
-        n.alpha = idleAge > 22 ? Math.max(0, n.alpha - dt * 0.5) : Math.min(1, n.alpha + dt * 2);
+        const window = landmark ? 60 : 22;
+        n.alpha =
+          idleAge > window
+            ? Math.max(0, n.alpha - dt * 0.5)
+            : Math.min(1, n.alpha + dt * 2);
         if (n.alpha <= 0.02) this.nodes.delete(n.id);
       }
     }