fix: restore agent mentions and child permission auto-accept

Sends tagged agents as OpenCode agent parts
Auto-accepts pending child-session permissions from parent sessions

packages/ui/src/sync/session-ui-store.ts

@@ -67,6 +67,7 @@ function routeMessage(params: {
   providerID: string
   modelID: string
   agent?: string
+  agentMentionName?: string
   variant?: string
   inputMode?: "normal" | "shell"
   files?: Array<{ type: "file"; mime: string; url: string; filename: string }>
@@ -133,6 +134,7 @@ function routeMessage(params: {
       modelID: params.modelID,
       text: params.content,
       agent: params.agent,
+      agentMentions: params.agentMentionName ? [{ name: params.agentMentionName }] : undefined,
       variant: params.variant,
       files: params.files,
       additionalParts: params.additionalParts,
@@ -785,6 +787,7 @@ export const useSessionUIStore = create<SessionUIState>()((set, get) => ({
         providerID,
         modelID,
         agent: effectiveDraftAgent,
+        agentMentionName,
         variant,
         inputMode,
         files,
@@ -860,6 +863,7 @@ export const useSessionUIStore = create<SessionUIState>()((set, get) => ({
       providerID,
       modelID,
       agent: effectiveAgent,
+      agentMentionName,
       variant,
       inputMode,
       files,