feat(daemon): expose watching over the RPC surface and the CLI

The watch subscription was reachable only from the library. It is most
useful against a daemon -- that is the session that stays connected long
enough to receive the server's status pushes -- so it needs the wire.

- proto: user.watch / user.unwatch / user.watched, with a Watched response
- SessionApi gains watch_user / unwatch_user / watched_users, so a local and
  a remote session are still interchangeable above the seam
- CLI: `watch add`, `watch remove`, `watch list`, documented in SKILL.md
  including the caveat that a one-shot run's watch ends with the run
- docs/openrpc.json regenerated from the wire types

soulseek-rs/src/remote/mod.rs

@@ -15,7 +15,7 @@ use crate::daemon::proto::{
     Members, MessageParams, Messages, Method, PROTOCOL_VERSION, QueryParams,
     Request, Response, RoomRef, RpcError, SayParams, SearchResults, Searches,
     Seconds, SharesStatus, SlotsParams, TransferRef, Uploads, UserRef,
-    UserResult,
+    UserResult, Watched,
 };
 use mirror::Mirror;
 use serde::de::DeserializeOwned;
@@ -757,6 +757,30 @@ impl SessionApi for RemoteSession {
         )
     }
 
+    fn watch_user(&self, username: &str) -> Result<()> {
+        self.tell(
+            Method::UserWatch,
+            UserRef {
+                username: username.to_string(),
+            },
+        )
+    }
+
+    fn unwatch_user(&self, username: &str) -> Result<()> {
+        self.tell(
+            Method::UserUnwatch,
+            UserRef {
+                username: username.to_string(),
+            },
+        )
+    }
+
+    fn watched_users(&self) -> Vec<String> {
+        self.request::<_, Watched>(Method::UserWatched, ())
+            .map(|watched| watched.users)
+            .unwrap_or_default()
+    }
+
     fn user_info(&self, username: &str) -> Option<UserInfo> {
         self.request::<_, UserResult>(
             Method::UserInfoOf,