Approve the News and Activity stream definitions #272

Part of #271 (Phase 1).

Question. Do we adopt the stream definitions in #265 as the site's rule for what goes where?

The text to approve is the README's "News and Activity" section at 44f5479. The bullets below summarise it.

• News is announcements people write: new projects, grants and funding, people, workshops, tutorials and talks, partnerships, and changes that affect users.
• Activity is written by the reporter: every library release, changes to existing lecture series, and updates to translated editions.
• Excluded from both: dependency and CI changes, analytics, metadata, translation-sync tooling, and website changes.
• Promotion is a human decision: anything in Activity can also get a News post written by a person.

The definitions describe the type of information only. Where each stream appears is decided in #266.

Options.

1. Approve as written.
2. Amend them, saying what changes.
3. Reject them, and keep the bot's posts on News.

Lean: approve.

• John's comment on Split updates into News and an Activity feed #265 says he's "happy with the arrangement above, as long as something gets posted regularly and we don't have to do much work!"
• The set-and-forget note explains how daily, self-merging Activity updates meet that.

How it closes. Record the choice here and close as completed. An approving review on #265 is the natural signal.