Let more than one story break at a time

[ssavutu]

From this morning's Slack: DragonFly went out, the Academy story broke an hour
later, and there was nowhere to put it. The banner shows one story, and pinning
the second would have taken the first one down. Erik asked for both; Audrey's
workaround was to wait a day.

Banner

GetBreakingNewsState now returns every published flagged article, newest
first, capped at 3. The cap is about how long a reader waits for a headline to
come back around on a scrolling banner, not about width.

Backward compatible on purpose. The response keeps enabled, text and
article_slug describing the newest story and adds items beside them:

"breaking_news": {
  "enabled": true,
  "text": "DragonFly story",
  "article_slug": "dragonfly",
  "items": [
    { "text": "DragonFly story", "article_slug": "dragonfly" },
    { "text": "Academy story",   "article_slug": "academy" }
  ]
}

Scalene reads those three fields today (index.astro:19-21), so it keeps
rendering the newest story until it learns about items. No window where the
banner is blank because one repo deployed before the other. The manual banner
is an item too, so a reader can treat items as the whole banner.

Pins

priority is no longer exclusive. The three ClearFeaturedExcept call sites
are gone along with the functions, so nothing takes a pin down on an editor's
behalf. Pinned stories lead the homepage newest-first, up to 3.

Per your call: recency decides the order, the toggle decides what is in the
running. An editor who wants the older story on top unpins the newer one.

Editor UI

Settings lists every story on the banner with a link to each article, since an
editor wondering why their headline is not up needs to see the ones that are.
Both checkbox blurbs now state the cap instead of "only one article can be
featured".

Not in this PR

The public site still renders one banner story and one lead card. Scalene needs
the marquee and the second lead slot before any of this is visible; happy to do
that next.

Verification

go test -p 1 ./... against a real MariaDB 11.8 with CMS_TEST_DSN, so the
integration tests actually ran rather than skipping. Plus go vet, tsc --noEmit, vitest (20), and swag init regenerated.

New tests: banner ordering, banner cap, manual-banner-as-item, settings listing
both stories, pin ordering, pin cap, and the homepage end-to-end with two pins.
The old exclusivity test now asserts the opposite.

🤖 Generated with Claude Code

https://claude.ai/code/session_01L4qBhBdQto1yNp1zP7VLYc