feed: viewer mute/block — mute actors/tags/objects + apply-prefs bag + 9 tests

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plans/feed-on-sx.md

@@ -14,7 +14,7 @@ APL, ACL visibility filtering via `lib/acl/`, federation via fed-sx.
 
 ## Status (rolling)
 
-`bash lib/feed/conformance.sh` → **154/154** (Phases 1–4 + TF-IDF + notifications + home + smart-dedupe + trending)
+`bash lib/feed/conformance.sh` → **163/163** (Phases 1–4 + TF-IDF, notifications, home, smart-dedupe, trending, mute)
 
 ## Ground rules
 
@@ -154,6 +154,9 @@ are function parameters. Real acl-sx / fed-sx wire in at the call site unchanged
 - [x] Trending — `feed/trending` / `feed/trending-actors`: objects/actors ranked
   by activity count in a recency window, count-desc with key-asc tiebreak
   (`trending.sx`); 11 tests. (154/154 total.)
+- [x] Mute/block — `feed/mute-actors` / `feed/mute-tags` / `feed/mute-objects` /
+  `feed/apply-prefs`: viewer-controlled per-request filtering (complements ACL's
+  author-controlled visibility) (`mute.sx`); 9 tests. (163/163 total.)
 
 (none)