Stop Following VF from scoring quoted posts at TimelineHome

[Pitchfork-and-Torch]

Bug

Following reverse-chron fetches every attached post at TimelineHome, including quoted tweets and conversation ancestors. For You already fetches those ids at TimelineHomeRecommendations.

NSFW_HIGH_PRECISION, DO_NOT_AMPLIFY, spam-high-recall, and the other OON-only Drop rules are Interstitial (or Allow) on Home and Drop on Recs. should_drop_ancillary only treats Action::Drop. AncillaryVFFilter is on the Following post-selection path.

A followee quoting an NSFW / DoNotAmplify post therefore survives Following, while the same quote is dropped on For You.

• Entry: VFFollowingCandidateHydrator collects tweet_id, ancestors, quoted_tweet_id, retweeted_tweet_id into one vec and calls get_result(..., TimelineHome, ...)
• Sink: AncillaryVFFilter (drop_ancillary_posts)
• Break: quoted/ancestor ids never see Recs Drop rules
• Viewer effect: Following shows a followee quote of a post For You would hard-drop
• Twin: VFCandidateHydrator (Phoenix / For You) already puts quotes and ancestors on TimelineHomeRecommendations

This is not PR 55 (For You dual-role HashMap merge). This is not PR 90 (two-map residual on that hydrator). This is not fail-open on miss.

Fix

Keep Following primaries (and retweet originals) on TimelineHome. Fetch quotes and ancestors on TimelineHomeRecommendations. Do not collapse the two maps: primary visibility reads Home, ancillary drop reads Recs (quotes/ancestors) and Home (retweet originals, unchanged).

Tests

• Quote whose Recs verdict is Drop and Home verdict is Interstitial -> drop_ancillary_posts = true; primary stays Interstitial
• Ancestor Recs Drop -> ancillary drop
• Followee NSFW primary with Recs Drop on the same id -> still Interstitial, not ancillary-dropped
• Retweet original stays on Home (Following RT amplification unchanged this PR)

cargo: cannot run. Public dump has no Home Mixer manifest.

Still-open leftover

For You still pushes retweeted_tweet_id onto the Home vec even when the wrapper is OON. Separate class. Do not mix it here.