FeedFeedback fixes (#3968)

* Lower seen threshold to 1.5s

* Send feedContext for replies

* Use a simpler and more reliable feedContext fallback

---------

Co-authored-by: Paul Frazee <pfrazee@gmail.com>

src/lib/api/feed-manip.ts

@@ -71,6 +71,10 @@ export class FeedViewPostsSlice {
       ?.__source as ReasonFeedSource
   }
 
+  get feedContext() {
+    return this.items.find(item => item.feedContext)?.feedContext
+  }
+
   containsUri(uri: string) {
     return !!this.items.find(item => item.post.uri === uri)
   }