fix(desktop): keep pinned + recent sessions visible across compression

Long-running sessions auto-compress: the gateway ends the original session
and surfaces the live continuation under a new id (list_sessions_rich projects
the root forward to its tip). Two symptoms fell out of the id rotation:

- A pinned session "vanished" — the pin is stored as the pre-compression root
  id, but the sidebar only matched on the live id, so it was filtered out.
  Pins now resolve on the durable lineage-root id (`_lineage_root_id`, already
  surfaced by the projection): the sidebar indexes sessions by both ids, pin/
  unpin and reorder operate on the durable id, and `sessionPinId()` is shared
  with the Cmd+P toggle. Existing pins keep working with no migration.

- A freshly-continued session was missing from the list until you ungrouped +
  "load 50 more" — the list paginated by original start time, so an old-but-
  active conversation sat past the first page. The desktop now requests
  `order=recent` (GET /api/sessions gains an `order` param backed by the
  existing recency CTE), surfacing live continuations on the first page.

hermes_cli/web_server.py

@@ -1363,6 +1363,7 @@ async def get_sessions(
     offset: int = 0,
     min_messages: int = 0,
     archived: str = "exclude",
+    order: str = "created",
 ):
     """List sessions.
 
@@ -1370,12 +1371,22 @@ async def get_sessions(
     ``exclude`` (default) hides them, ``only`` returns just the archived ones
     (used by the desktop "Archived sessions" settings panel), and ``include``
     returns both.
+
+    ``order`` controls pagination order: ``created`` (default, by original
+    start time) or ``recent`` (by latest activity across the compression
+    chain). ``recent`` keeps a long-running conversation on the first page
+    after it auto-compresses into a fresh continuation id.
     """
     if archived not in ("exclude", "only", "include"):
         raise HTTPException(
             status_code=400,
             detail="archived must be one of: exclude, only, include",
         )
+    if order not in ("created", "recent"):
+        raise HTTPException(
+            status_code=400,
+            detail="order must be one of: created, recent",
+        )
     try:
         from hermes_state import SessionDB
         db = SessionDB()
@@ -1389,6 +1400,7 @@ async def get_sessions(
                 min_message_count=min_message_count,
                 include_archived=include_archived,
                 archived_only=archived_only,
+                order_by_last_active=order == "recent",
             )
             total = db.session_count(
                 min_message_count=min_message_count,