Fix build warnings across workspace

- Remove redundant token fields from StreamEvent::Finished (data
  already delivered via Usage event)
- Remove dead hotkey_adjust_sampling, MAX_HISTORY, now()
- Fix unused variable warnings (delta, log)
- Suppress deserialization-only field warnings (jsonrpc, role)
- Make start_stream/chat_completion_stream_temp pub(crate)
- Remove unnecessary pub(crate) re-export of internal types

Remaining warnings are TODO items: SkipIndex (scoring not wired),
notify (MCP notifications not wired).

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/claude/mcp-server.rs

@@ -13,6 +13,7 @@ use std::io::{self, BufRead, Write};
 
 #[derive(Deserialize)]
 struct Request {
+    #[allow(dead_code)]
     jsonrpc: String,
     method: String,
     #[serde(default)]