fix: view-queue link + agent inbox shows unread messages only

fix(dashboard): update 'view queue' link to /builds.html

The build queue moved to its own /builds.html page. The queue-summary
'view queue →' link in tabs.js still pointed at /core.html, so clicking
it landed on the wrong page.

fix(broker): filter agent inbox to unread (acked_at IS NULL)

recent_for was returning all messages regardless of ack state, so the
agent inbox showed everything even after 'mark all read'. Now filters
to acked_at IS NULL — mirroring exactly what mark_all_read drains —
so the inbox empties on reload after the operator drains it.

hive-c0re/src/broker.rs

@@ -339,9 +339,9 @@ impl Broker {
         Ok(batch)
     }
 
-    /// Latest `limit` messages addressed to `recipient`, newest-first.
-    /// Includes delivered + undelivered alike — used for the operator
-    /// inbox view on the dashboard. Caller decides what to show.
+    /// Unread (unacked) messages addressed to `recipient`, newest-first.
+    /// Filters to `acked_at IS NULL` so the agent inbox view clears after
+    /// "mark all read" — mirroring exactly what `mark_all_read` will drain.
     pub fn recent_for(&self, recipient: &str, limit: u64) -> Result<Vec<InboxRow>> {
         let conn = self.conn.lock().unwrap();
         let limit_i = i64::try_from(limit.min(i64::MAX as u64)).unwrap_or(i64::MAX);
@@ -349,6 +349,7 @@ impl Broker {
             "SELECT id, sender, body, sent_at, in_reply_to
                FROM messages
               WHERE recipient = ?1
+                AND acked_at IS NULL
               ORDER BY id DESC
               LIMIT ?2",
         )?;