Pre-meeting Slack briefings with HubSpot context, 15 minutes ahead

Build me an agent workflow that DMs me on Slack a short pre-meeting briefing about 15 minutes before every external meeting on my calendar.

Trigger: cron every 15 minutes, weekdays only, during business hours (Mon-Fri, roughly 7am to 6pm local time). Aurinko is not in the poll-provider catalog, so a cron cadence is the right shape.

Each run should do the following:

1. Call Aurinko List Events In Range with calendar id `primary` to fetch events starting in the next 15 to 45 minutes. Pass ISO 8601 timeMin and timeMax with the local timezone offset (Aurinko requires timezone-aware ISO 8601).

2. Keep only meetings that have at least one external attendee (attendee email domain differs from my own). Track which event ids have already been briefed on prior runs and skip those so I never get pinged twice for the same meeting.

3. For each remaining meeting:

a. Extract external attendee email addresses.

b. Look each attendee up in HubSpot with Search Contacts. For matched contacts, pull the associated company and any open deals via HubSpot Search Deals. Surface deal stage, amount, close date, and owner.

c. Call Aurinko List Email Messages to fetch up to the last 5 emails exchanged with those attendees, so the briefing can quote the most recent thread subject plus a one-line summary.

d. Compose a concise briefing: meeting title and start time, attendees with title and company, deal context (stage / amount / close date / owner), 1 to 3 recent email highlights, and one suggested talking point or question.

e. Post it to me as a Slack DM using Slack Bot Send a Message. Exactly one Slack message per meeting.

Constraints: this workflow is read-only. Do not write anything back to HubSpot, do not modify the calendar, do not send email. The only side effect is the Slack DM.

Keep briefings tight. If there is nothing useful to say (no HubSpot match, no recent email), still send a lightweight heads-up so I know the meeting is coming up. Aurinko is the right calendar and email integration here because a single connection covers Gmail, Outlook, Exchange, and iCloud, so this works for any mailbox provider.