feat(escalations): close out plan-locked wedge polish

Four items from the design-plan audit, all flagged as locked-design or
Codex corrections, shipped together so the GTM demo path covers them
end-to-end before bug bash.

1. Live AI assessment refresh on the magic-moment screen. Backend already
   publishes handoff_assessment_ready when enrich_escalation_async commits;
   wire the frontend listener so the senior sees the assessment populate
   without a manual reopen. New event type + onAssessmentReady handler on
   streamEscalations; AssistantChatPage opens a scoped SSE subscription
   whenever it tracks a handoff missing its assessment, refetches on match,
   and replaces magicHandoff / overlayHandoff in place. Closes the loop on
   the async-assessment commit e8ba74e.

2. Suggested-step chips below the chat input. Locked design from the plan
   (Codex correction). Chip strip renders above the composer post-claim
   when ai_assessment_data.suggested_steps[] is non-empty. Click prefills
   the input and focuses; first send or explicit X hides for the session.

3. Unread 6px dot on EscalationQueue cards. localStorage-persisted seen
   set (rf-escalation-seen, capped 200). Dot top-right when not seen.
   Cleared on open (card click) or claim (Pick Up) — NOT on hover, per
   Codex correction. Pick Up stops propagation so it doesn't double-fire.

4. Race-condition toast on claim conflict. The /claim endpoint previously
   silently overwrote claimed_by — both seniors thought they owned the
   session. New HandoffAlreadyClaimedError carries the winner's id/name/
   timestamp; claim_session rejects different-user re-claims (same-user is
   idempotent for double-click safety); endpoint returns 409 with
   structured detail. AssistantChatPage.handleStartHere extracts and
   surfaces "Already claimed by {name} {time_ago}." via toast, drops
   ?pickup=true, dismisses magic-moment so the loser flows back to queue.

Tests: 2 new unit tests in test_handoff_manager.py (conflict raises,
same-user idempotent). Full handoff + escalation suite (34 tests) green.
Frontend tsc -b clean.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/api/aiSessions.ts

@@ -19,6 +19,7 @@ import type {
   ChatMessageRequest,
   ChatMessageResponse,
   HandoffCreatedEvent,
+  HandoffAssessmentReadyEvent,
   EscalationStreamHandlers,
 } from '@/types/ai-session'
 
@@ -279,6 +280,13 @@ export const aiSessionsApi = {
           const parsed = JSON.parse(data) as Record<string, unknown>
           if (eventType === 'handoff_created' && parsed.type === 'handoff_created') {
             handlers.onHandoffCreated?.(parsed as unknown as HandoffCreatedEvent)
+          } else if (
+            eventType === 'handoff_assessment_ready' &&
+            parsed.type === 'handoff_assessment_ready'
+          ) {
+            handlers.onAssessmentReady?.(
+              parsed as unknown as HandoffAssessmentReadyEvent,
+            )
           } else if (eventType === 'ready') {
             handlers.onReady?.()
           }