feat(security): require the node password to grant Trusted

Promotion to Trusted is a privilege escalation — a Trusted peer can read
node state, be deployed to, and is exempt from the `!= Untrusted` gates
federation/DWN/messaging use. It must therefore cost a fresh proof that
the person at the keyboard is the operator, not merely that a session
cookie exists. Same reasoning as node.rotate-identity and TOTP setup,
both of which already re-verify.

Both entry points are covered:

- `federation.invite` gates on the RESOLVED level, not on an explicit
  request for Trusted: "Link Your Nodes" sends no `trust_level` at all
  and falls through to the Trusted default. The invite is a bearer grant
  of Trusted to whoever redeems it, so minting it IS the escalation.
  Observer invites are untouched.
- `federation.set-trust` gates only when the peer is not already
  Trusted, so the dropdown re-emitting its own value doesn't demand a
  password for a no-op.

Demotion is deliberately NOT gated: making something less privileged
must never be harder than leaving it alone, or the safe action becomes
the inconvenient one.

The backend is the sole authority on what counts as an escalation — it
returns a `PASSWORD_REQUIRED:`-prefixed error and the UI prompts and
retries only on that, so the rule lives in exactly one place and the
frontend never pre-judges. TrustPasswordModal.vue (modelled on
RotateDidModal.vue) serves both flows. NodeDetailModal's select snaps
back to the node's real level on change, since a cancelled or failed
promotion would otherwise leave the dropdown displaying a level the node
never accepted.

The operator path stamps TrustSource::Manual; set_trust_level grew an
`Option<TrustSource>` so automatic adjustments (the discovery-handshake
demotion safety net) pass None and leave the recorded provenance alone
rather than laundering an uninvited-join peer into looking approved.

Follow-up, deliberately out of scope: `federation.join` also reaches
Trusted when redeeming someone else's Trusted invite, with no re-auth.

Tests: 44/44 federation, 79/79 rpc-client, vue-tsc clean.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

neode-ui/src/views/federation/NodeDetailModal.vue

@@ -26,7 +26,7 @@
           <div class="flex items-center gap-2 mt-1">
             <select
               :value="node.trust_level"
-              @change="emit('change-trust', node!.did, ($event.target as HTMLSelectElement).value)"
+              @change="onTrustChange"
               class="bg-black/30 text-white text-sm rounded px-2 py-1 border border-white/10"
             >
               <option value="trusted">Trusted</option>
@@ -34,6 +34,9 @@
               <option value="untrusted">Blocked</option>
             </select>
           </div>
+          <p class="text-xs text-white/40 mt-2">
+            <span class="text-white/30">Granted via:</span> {{ trustSourceLabel }}
+          </p>
         </div>
         <div class="bg-white/5 rounded-lg p-3">
           <p class="text-xs text-white/40 mb-1">Added</p>
@@ -130,7 +133,7 @@
 </template>
 
 <script setup lang="ts">
-import { ref } from 'vue'
+import { computed, ref } from 'vue'
 import type { FederatedNode } from './types'
 import { formatBytes, formatUptime } from './utils'
 
@@ -156,6 +159,32 @@ const emit = defineEmits<{
 const confirmRemove = ref(false)
 const deployAppId = ref('')
 
+const TRUST_SOURCE_LABELS: Record<string, string> = {
+  invite: 'An invite you minted',
+  'uninvited-join': 'Joined without an invite — capped at Observer',
+  'transitive-merge': 'Advertised by another peer — capped at Observer',
+  manual: 'You set it here',
+}
+
+/** Unknown provenance is stated plainly rather than hidden: a peer recorded
+ *  before this was tracked is precisely the one worth a second look. */
+const trustSourceLabel = computed(
+  () => TRUST_SOURCE_LABELS[props.node?.trust_source ?? ''] ?? 'Unknown — recorded before this was tracked',
+)
+
+/** Snap the select back to the node's actual level immediately. Promoting to
+ *  Trusted asks for the node password, and the operator may cancel or get it
+ *  wrong — without this the dropdown would keep displaying a level the node
+ *  never accepted. On success the parent reloads and the prop drives the new
+ *  value back in. */
+function onTrustChange(event: Event) {
+  const select = event.target as HTMLSelectElement
+  const level = select.value
+  if (!props.node) return
+  select.value = props.node.trust_level
+  emit('change-trust', props.node.did, level)
+}
+
 function handleClose() {
   confirmRemove.value = false
   deployAppId.value = ''

neode-ui/src/views/federation/TrustPasswordModal.vue

@@ -0,0 +1,74 @@
+<template>
+  <Teleport to="body">
+    <Transition name="modal">
+      <div v-if="visible" class="fixed inset-0 z-[3000] flex items-center justify-center p-4" @click.self="handleClose">
+        <div class="absolute inset-0 bg-black/60 backdrop-blur-sm"></div>
+        <div class="glass-card p-6 max-w-md w-full relative z-10">
+          <h3 class="text-lg font-semibold text-white mb-2">Confirm Trusted Access</h3>
+          <p class="text-sm text-white/60 mb-4">{{ context }}</p>
+          <input
+            ref="passwordInput"
+            v-model="password"
+            type="password"
+            autocomplete="current-password"
+            placeholder="Enter your node password to confirm"
+            class="w-full bg-black/30 border border-white/10 rounded-lg px-3 py-2 text-sm text-white placeholder-white/30 focus:outline-none focus:border-orange-500/50 mb-4"
+            @keyup.enter="submit"
+          />
+          <p v-if="error" class="text-red-400 text-xs mb-3">{{ error }}</p>
+          <div class="flex gap-3">
+            <button @click="handleClose" class="flex-1 glass-button px-4 py-2 rounded-lg text-sm">Cancel</button>
+            <button
+              @click="submit"
+              :disabled="busy || !password"
+              class="flex-1 glass-button px-4 py-2 rounded-lg text-sm font-medium bg-orange-500/20 border-orange-500/30 disabled:opacity-50"
+            >
+              {{ busy ? 'Verifying…' : 'Grant Trusted' }}
+            </button>
+          </div>
+        </div>
+      </div>
+    </Transition>
+  </Teleport>
+</template>
+
+<script setup lang="ts">
+import { ref, nextTick, watch } from 'vue'
+
+const props = defineProps<{
+  visible: boolean
+  /** What is about to be granted, in the operator's terms. */
+  context: string
+  busy: boolean
+  error: string
+}>()
+
+const emit = defineEmits<{
+  close: []
+  confirm: [password: string]
+}>()
+
+const password = ref('')
+const passwordInput = ref<HTMLInputElement | null>(null)
+
+function submit() {
+  if (!password.value || props.busy) return
+  emit('confirm', password.value)
+}
+
+function handleClose() {
+  password.value = ''
+  emit('close')
+}
+
+// Never leave the password sitting in memory once the modal is dismissed,
+// and put the cursor where the operator has to type anyway.
+watch(() => props.visible, async (val) => {
+  if (!val) {
+    password.value = ''
+    return
+  }
+  await nextTick()
+  passwordInput.value?.focus()
+})
+</script>

neode-ui/src/views/federation/types.ts

@@ -40,6 +40,13 @@ export interface FederatedNode {
   last_sync_error?: string
   /** RFC 3339 timestamp of last_sync_error. */
   last_sync_error_at?: string
+  /**
+   * How this peer's trust level came to be what it is. `null` means it was
+   * recorded before provenance was tracked — which is exactly the population
+   * worth reviewing, since it may include grants made by the fail-open paths
+   * that `uninvited-join` / `transitive-merge` now cap at Observer.
+   */
+  trust_source?: 'invite' | 'uninvited-join' | 'transitive-merge' | 'manual' | null
 }
 
 export interface DwnStatus {