Record @mention wake failures instead of silently swallowing them

The catch block in wakeAgentMentions now records wake_state on each
mention (woken/failed) instead of silently discarding the error. Failed
mentions render with a strikethrough and muted color so the user sees
which agents could not be reached, with a tooltip on hover. Migration
044 adds the wake_state column to chat_mentions.

AgentCompany-New/src/shared/chat-domain.ts

@@ -62,6 +62,7 @@ export interface ChatMentionRecord {
   targetId: string;
   offsetStart: number;
   offsetEnd: number;
+  wakeState: "none" | "woken" | "failed";
 }
 
 export interface ChatSlashInvocationRecord {