refactor(operator): remove fake on-call pill from topbar

The "on-call · Mikkel" pill named a person who doesn't exist and a paging
system we haven't built. The IncidentModal still says "will notify on-call"
but nothing actually does, and no schema for rotations / pages exists in
platform-api. Showing this in the chrome was claiming an operational fact
that isn't true.

Drop the prop, span, and CSS from OpTopbar. The right cluster becomes
just [bell] [profile].

Mock audit + incident-timeline fixtures still carry historical "on-call
paged" entries — those are records of past events in the mock, not live
state, so they stay. Paging gets a real indicator when the incident
backend lands (tracked as "Real on-call indicator" in NEXT-STEPS.md).

apps/operator/components/OpTopbar.vue

@@ -1,6 +1,4 @@
 <script setup lang="ts">
-withDefaults(defineProps<{ oncall?: boolean }>(), { oncall: true })
-
 const { open: openPalette } = useCommandPalette()
 const { env } = useEnv()
 
@@ -25,11 +23,6 @@ const ENVS = {
     </button>
 
     <div class="right">
-      <span class="oncall" :class="{ active: oncall }">
-        <StatusDot :color="oncall ? 'var(--accent)' : 'var(--text-mute)'" :size="6" :glow="false" />
-        <Mono :dim="!oncall">{{ oncall ? 'on-call · Mikkel' : 'no active page' }}</Mono>
-      </span>
-
       <button class="icon-btn" title="Notifications">
         <UiIcon name="bell" :size="14" />
         <span class="icon-btn-dot" />
@@ -106,18 +99,6 @@ header {
   flex-shrink: 0;
 }
 
-.oncall {
-  display: inline-flex;
-  align-items: center;
-  gap: 8px;
-  padding: 4px 10px;
-  border: 1px solid var(--border);
-  border-radius: 4px;
-  white-space: nowrap;
-  flex-shrink: 0;
-}
-.oncall.active { background: rgba(212, 255, 58, 0.1); border-color: rgba(212, 255, 58, 0.3); }
-
 .icon-btn {
   position: relative;
   height: 32px;