fix(web): a scheduled run reports to the person who deployed it (CL-8580)

[TheGreatAxios]

Summary

• A cron-scheduled agent run's mail body previously carried no reachable sender, so the ticker's mail address (cron@<domain>) has no mailbox and the agent's reply is silently dropped by the hub.
• The scheduled run's body now names the deploying person's mailbox address and asks the agent to reply there.

Changes

• apps/web/src/agent-deploy.ts: scheduleAgentRun resolves the deploying person's mailbox address (<refId>@<tenantDomain>, same shape threads-api.ts builds a person participant's address from) via the existing session probe, and passes it into a new buildScheduledRunBody helper that asks the agent to mail its result there (as a single-item to list) with a short subject. Falls back to a bare reply instruction if the session probe comes back empty — never fails the deploy over it.

Testing

• bun test apps/web/src/agent-deploy.test.ts
• bun run check

[linear-code]

CL-8580