Post is not relayed when published via `Announce` activity

I am trying to publish a post to https://relay.fedi.buzz using the `Announce` activity (LitePub relay protocol / https://github.com/astro/buzzrelay/issues/79 / 38f5b2cb139031703fbbddf8697e4756e2601bcb). The server responds with status 202, but the hashtag actor doesn't `Announce` the post back to my actor.

Example of activity:

```json
{"@context":["https://www.w3.org/ns/activitystreams","https://w3id.org/security/v1","https://w3id.org/security/data-integrity/v2",{"Emoji":"toot:Emoji","EmojiReact":"litepub:EmojiReact","Hashtag":"as:Hashtag","litepub":"http://litepub.social/ns#","sensitive":"as:sensitive","toot":"http://joinmastodon.org/ns#"}],"actor":"https://mitra.social/users/silverpill","cc":[],"id":"https://mitra.social/activities/announce/019c86d8-872e-4d55-8372-d982d98ee39e","object":"https://mitra.social/objects/019c76c5-cacd-e227-e739-24c2420f71e6","published":"2026-02-22T19:34:23.291471438Z","to":["https://relay.fedi.buzz/tag/activitypub"],"type":"Announce"}
```

The post has `#activitypub` hashtag. Activity is delivered to `https://relay.fedi.buzz/tag/activitypub` inbox.

Start by tracing how the relay handles the Announce activity delivered to the tag/activitypub inbox, using the example activity and the linked LitePub relay protocol issue and commit as context. Done means a post announced to the hashtag actor is relayed back to the originating actor as expected.

Written by the indexing model from the issue text.