feat(protocol): away status, excluded phrases, queue-place requests

Three features the client half-had. SetStatus (28) was only ever sent as
"online" at login, so there was no way to go away; excluded search phrases
(160) were parsed and logged into nowhere, so every client kept spending
searches on queries the server was never going to answer; and a queued
download could answer a peer asking about its place but could never ask
about its own.

Each is now driven end to end: the away status seen by another user, a
refused query on a stub server that announces phrases (soulfind keeps its
filters in a database the suite cannot seed), and a peer's answer landing
on the download as its queue position.

soulseek-rs-lib/src/client/search.rs

@@ -62,6 +62,9 @@ impl Client {
         let Some(handle) = &self.server_handle else {
             return Err(SoulseekRs::NotConnected);
         };
+        if let Some(phrase) = self.excluded_phrase_in(query) {
+            return Err(SoulseekRs::SearchPhraseExcluded(phrase));
+        }
         let token = next_search_token();
 
         self.context.write_safe()?.searches.insert(
@@ -119,6 +122,9 @@ impl Client {
         if self.server_handle.is_none() {
             return Err(SoulseekRs::NotConnected);
         }
+        if let Some(phrase) = self.excluded_phrase_in(query) {
+            return Err(SoulseekRs::SearchPhraseExcluded(phrase));
+        }
         let token = next_search_token();
         self.context.write_safe()?.searches.insert(
             query.to_string(),
@@ -130,6 +136,26 @@ impl Client {
         Ok(token)
     }
 
+    /// The phrases the server refuses to search for (code 160), as last
+    /// announced. Empty until the server has said.
+    #[must_use]
+    pub fn excluded_search_phrases(&self) -> Vec<String> {
+        self.context
+            .read_safe()
+            .map(|ctx| ctx.excluded_search_phrases())
+            .unwrap_or_default()
+    }
+
+    /// The excluded phrase `query` carries, if any — what a search would be
+    /// refused for.
+    #[must_use]
+    pub fn excluded_phrase_in(&self, query: &str) -> Option<String> {
+        self.context
+            .read_safe()
+            .ok()
+            .and_then(|ctx| ctx.excluded_phrase_in(query))
+    }
+
     /// Let responses accumulate for `timeout`, or until cancelled.
     ///
     /// Peers answer a search over their own connections whenever they get round