fix: pass assistantName to container agent instead of hardcoding 'Andy'

The container agent-runner had 'Andy' hardcoded as the sender name in
archived conversation transcripts. This ignored the configurable
ASSISTANT_NAME setting, so users who changed their assistant's name
(via .env or config) would still see 'Andy' in transcripts.

- Add assistantName field to ContainerInput interface (both host and
  container copies)
- Pass ASSISTANT_NAME from config through to container in index.ts
  and task-scheduler.ts
- Thread assistantName through createPreCompactHook and
  formatTranscriptMarkdown in the agent-runner
- Use 'AssistantNameMissing' as fallback instead of 'Andy' so a
  missing name is visible rather than silently wrong

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/container-runner.ts

@@ -42,6 +42,7 @@ export interface ContainerInput {
   chatJid: string;
   isMain: boolean;
   isScheduledTask?: boolean;
+  assistantName?: string;
   secrets?: Record<string, string>;
 }