refactor(federation): keyed diff-reconciled map scene — stable intro, smooth revisits

Root causes of the flaky intro / janky revisits, all fixed structurally:

- Graph updates now RECONCILE against the live scene by identity (peer DID /
  request id) instead of wiping the SVG: in-place updates for label/online/
  trust changes, animated arrivals for new nodes, animated departures for
  removed ones, and short-way-around slot glides when the ring layout shifts.
  The old wipe-and-rebuild orphaned every in-flight intro tween whenever the
  5s poll or the async self-DID fetch landed mid-intro — that was the
  'sometimes parts don't show'.
- The intro is gated on readiness: first real container measurement (post-
  layout, via ResizeObserver) AND the self node being present, with a 1.2s
  fallback. Graph changes during the intro queue and apply on completion.
- Layout is deterministic per node: peers sort by DID for slot assignment and
  jitter/phase hash from the DID, so backend response order can't shuffle
  the map between polls.
- The long cinematic intro plays once per browser session; revisits get a
  shorter, lighter entrance that doesn't fight the route transition.
- selfDid seeds from the cached localStorage value (re-cached on fetch) so
  the centre node and links exist from the first frame.
- Requests' waiting-room orbit pushed clearly outside the peer rings (+1.0)
  with loose per-request hover jitter — outside until accepted, then the
  join animation glides them in.
- Full unmount hygiene: every tween killed by target (incl. the repeating
  sonar pulse), fallback timer cleared, window listeners removed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

neode-ui/src/views/Federation.vue

@@ -339,7 +339,13 @@ function onMapSelect(did: string) {
   if (node) selectedNode.value = node
 }
 
-const selfDid = ref('')
+/** Seeded from the cached DID so the map's centre node (and its links) exist
+ *  on the very first frame; the authoritative fetch in onMounted refreshes it
+ *  and re-caches. Without this the intro raced the RPC and often played with
+ *  no centre. */
+const selfDid = ref<string>((() => {
+  try { return localStorage.getItem('neode_did') || '' } catch { return '' }
+})())
 
 const mapNodes = computed(() => {
   const result = []
@@ -819,6 +825,7 @@ onMounted(async () => {
   try {
     const result = await rpcClient.getNodeDid()
     selfDid.value = result.did
+    try { localStorage.setItem('neode_did', result.did) } catch { /* private mode */ }
   } catch {
     // Self DID not available
   }