Add a permanent "Latest" lane beside "Highlights"

Restructure the nav around two permanent lanes, then the reader's chosen ones:
"Highlights" (the curated daily brief — formerly "Today") and "Latest" (the
freshest accepted stories, newest-first). Now that the gate is tight, a
chronological "incoming" feed is safe to expose.

* feed(): new sort="latest" (pure recency) alongside the default best-first
  rank; /api/feed exposes sort=ranked|latest (validated). Still accepted-only
  and boundary-respecting either way.
* lanes.py: two pinned lanes (Highlights + Latest) instead of one.
* Home: "Latest" view + "Load more" pagination for every feed view (offset-
  paged, de-duped). Mobile bottom bar gains a Latest tab.
* LanePicker shows both pinned lanes; nav rail renders them first.

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

goodnews/queries.py

@@ -57,8 +57,13 @@ def feed(
     max_cortisol: int | None = None,
     max_ragebait: int | None = None,
     tag: str | None = None,
+    sort: str = "ranked",
 ) -> list[dict]:
-    """Return ranked articles with categorical filters applied in SQL.
+    """Return articles with categorical filters applied in SQL.
+
+    sort="ranked" (default) is best-first by the composite rank; sort="latest"
+    is pure recency (newest first) for the chronological "Latest" feed. Both
+    stay accepted-only and respect the same boundaries.
 
     Categorical filters (topic/flavor include & mute, cortisol/ragebait ceilings)
     must be applied here, not after ranking — otherwise low-ranked-but-matching
@@ -105,6 +110,11 @@ def feed(
     where = "WHERE " + " AND ".join(clauses)
     params.extend([limit, offset])
 
+    order_by = (
+        "COALESCE(a.published_at, a.discovered_at) DESC, rank_score DESC"
+        if sort == "latest"
+        else "rank_score DESC, COALESCE(a.published_at, a.discovered_at) DESC"
+    )
     rows = conn.execute(
         f"""
         SELECT {_ARTICLE_COLUMNS}
@@ -112,7 +122,7 @@ def feed(
         JOIN sources src ON src.id = a.source_id
         JOIN article_scores s ON s.article_id = a.id
         {where}
-        ORDER BY rank_score DESC, COALESCE(a.published_at, a.discovered_at) DESC
+        ORDER BY {order_by}
         LIMIT ? OFFSET ?
         """,
         params,