Morrow Brief: social page channel (Buffer autopost + Telegram bot) - #3

What this adds

Morrow Brief: the published edition as a page channel. One morning digest of five stories plus a few alerts for stories that three or more outlets report. Every post carries its outlet count, a link and a typographic card.

• Telegram is posted to directly; Instagram, Threads and X go through Buffer.
• A Telegram bot answers section commands and /find (Cloudflare Worker webhook, or a cron poller as fallback).
• State, cards and feed.json live on a social-data branch, never on main.
• Nothing is posted until the secrets are set. Setup and failure handling: docs/SOCIAL.md.

Checked

• 123 Python tests, 13 Worker tests, and the 4 existing waitlist tests pass locally.
• A four-run rehearsal on today's edition (build, deliver without credentials, second build, next-day stale page).
• Hone loop, judged by a council of 3 models on a frozen rubric: v0 7.8, v2 8.25. Gates G1-G7 pass.

Not verified

• A real Buffer createPost, a real Telegram send, and the Worker deployed on Cloudflare. No accounts, key or token exist yet.
• Whether Buffer and Instagram accept card images served from raw.githubusercontent.com.
• Whether the generator's pushes trigger the push workflow (a 3-hour cron is the fallback).
• The publish job and the schedule, which only run on main after merge.

This PR does not touch index.html, waitlist.yml or keepalive.yml.