feat(federation): pass explicit intent at every ensurePeered call site

- social.ts friend-add: user_action, with 409 peer_pending_local_admin
  when gate fires
- /peer/ensure: user_action, surfaces peeringStatus: 'admin_required'
- sendCallRelay (typing warm-up + call relay): system intent
- federationWorker resolvePendingPeers: system intent (defensive — gate
  is unreachable from here since pending rows already exist)
- CallRelayFailureReason: peer_admin_required added (mapped to
  peer_transient_failure on the user-facing event surface, since system
  intent should never legitimately surface admin_required)
- Test files: thread intent arg through racePeering and ensurePeered
  calls (positional shift from racePeering signature change)
- outboundGate.test.ts: tighten noUncheckedIndexedAccess access via
  non-null assertions after toHaveLength()
- docs/systems/social.md: peer_pending_local_admin error code documented

packages/server/src/utils/federationWorker.ts

@@ -496,7 +496,7 @@ async function resolvePendingPeers(): Promise<void> {
   for (const { peerId, peerOrigin } of pendingWithEntries) {
     console.log(`[federation-worker] Attempting auto-peer with ${peerOrigin}...`);
 
-    const result = await ensurePeered(peerOrigin);
+    const result = await ensurePeered(peerOrigin, { kind: 'system' });
 
     switch (result.status) {
       case 'active':