Keep a just-read article visible (and Previous-reachable) until the next fetch

The Unread/Older views are live Room Flow queries filtered on
isRead = 0, so marking an article read (which only happens on
Next/Previous, not on open) makes it vanish from the list the instant
Room re-emits -- mid-scroll, or from underneath the reader's own
Previous button, which re-queries this same flow to find its
neighbors. Concretely: Next from C to D marks C read and prunes it
from the live list; Previous from D then can't find C anymore, and
jumps past it to whatever was unread before C. A misclick or the
in-flight prune could cost you the article you meant to keep reading.

Adds ArticleEntity.readAt (set whenever isRead flips true, cleared on
explicit "mark unread"); observeUnread/observeOlderUnread now match
"isRead = 0 OR readAt >= sinceFetch", where sinceFetch is
Settings.lastFetchAt -- the same durable signal the new-articles
snackbar already uses. A read article now lingers (shown dimmed via
the existing showReadState styling) until the next real fetch
actually completes, not the next DB write, and Previous/Next read from
the same still-inclusive query so stepping back to what you just read
finds it right where it was.

1 files changed, 1 insertions, 0 deletions

diff --git a/app/src/main/java/org/terst/feedreader/data/Entities.kt b/app/src/main/java/org/terst/feedreader/data/Entities.kt
index 5f6a28c..58c9f79 100644
--- a/app/src/main/java/org/terst/feedreader/data/Entities.kt
+++ b/app/src/main/java/org/terst/feedreader/data/Entities.kt
@@ -31,6 +31,7 @@ data class ArticleEntity(
     val extractedContent: String? = null,    // Readability-extracted full text, filled in on first read if feedContentHtml was thin
     val imageUrl: String? = null,            // thumbnail, from media:thumbnail/enclosure or the first <img> in the feed content -- see FeedParser
     val isRead: Boolean = false,
+    val readAt: Long? = null,                 // when isRead flipped true; null while unread or after an explicit "mark unread". Lets a just-read article linger in the Unread view until the next fetch instead of vanishing the instant it's read -- see observeUnread/observeOlderUnread.
     val isSaved: Boolean = false,             // explicitly kept (independent of read state) -- triggers a Stash save
     val stashArtifactId: String? = null,      // set once successfully archived to Stash; null means not yet saved or save failed
     val createdAt: Long