Drop replies whose conversation ancestors are muted or blocked

[Pitchfork-and-Torch]

Summary

AuthorSocialgraphFilter already drops when the viewer mutes or blocks the candidate author, and when the viewer blocks a quoted or retweeted author. Conversation modules still render ancestor tweets (root plus parent) from ancestor_users. Mute and block did not look at that list.

Brazil2026ElectionFilter already drops a reply when ancestor_users hits the listed-author set, with an explicit comment that ancestors are returned on the scored post for For You thread UI. This PR clones that ancestor edge for muted_user_ids and blocked_user_ids. One class, one file. No ranking changes.

This is not mute-on-quote (PR 23), not mute-on-retweet (PR 9), and not retweet original blocked-by (PR 100).

Proof

• Entry: CoreDataCandidateHydrator.build_ancestor_users writes candidate.ancestor_users (parent author plus root author)
• Sink: AuthorSocialgraphFilter (Phoenix pre-selection and Following reverse-chron post-selection)
• Break: mute/block matched author_id, quoted_user_id, and retweeted_user_id; ancestor_users was Brazil-only
• Viewer effect: F replies to muted or blocked user Q; Home still serves the reply and convo_marshaller includes Q's tweet in the conversation module (unless tombstoned)
• Twin: Brazil2026ElectionFilter.should_remove ancestor_users any(is_excluded); FollowingViewerMutedKeywordFilter already matches ancestor_texts

Test plan

• test_muted_ancestor_author_is_removed fails on main, passes on this branch
• test_blocked_ancestor_author_is_removed fails on main, passes on this branch
• test_unmuted_unblocked_ancestor_is_kept still keeps a reply whose ancestors are not muted or blocked
• unit tests added; cargo test cannot run in the public dump (no Home Mixer Cargo.toml)