mcp-server: auto-reconnect on broken pipe

When the daemon restarts, consciousness-mcp's socket connection goes
stale. Previously this caused all subsequent memory/journal tool calls
to fail with "Broken pipe" errors until manually restarted.

Now request() detects broken pipe/connection reset errors and
automatically reconnects to the daemon socket, re-initializes the
MCP session, and retries the request.

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

src/mcp-server.rs

@@ -127,7 +127,7 @@ impl DaemonClient {
         Ok(Self { reader, writer, next_id: 0 })
     }
 
-    fn request(&mut self, method: &str, params: Option<Value>) -> Result<Value, String> {
+    fn request_raw(&mut self, method: &str, params: Option<Value>) -> Result<Value, String> {
         self.next_id += 1;
         let req = json!({
             "jsonrpc": "2.0",
@@ -150,6 +150,40 @@ impl DaemonClient {
         }
         Ok(resp.result.unwrap_or(Value::Null))
     }
+
+    /// Re-establish connection to daemon and re-initialize.
+    fn reconnect(&mut self) -> Result<(), String> {
+        eprintln!("consciousness-mcp: reconnecting to daemon...");
+        let path = socket_path();
+        let stream = UnixStream::connect(&path)
+            .map_err(|e| format!("reconnect to {:?}: {}", path, e))?;
+        self.reader = BufReader::new(stream.try_clone().map_err(|e| e.to_string())?);
+        self.writer = BufWriter::new(stream);
+
+        // Re-initialize MCP session
+        self.request_raw("initialize", Some(json!({
+            "protocolVersion": "2024-11-05",
+            "capabilities": {},
+            "clientInfo": {"name": "consciousness-mcp", "version": "0.4.0"}
+        })))?;
+        let _ = self.request_raw("notifications/initialized", None);
+        eprintln!("consciousness-mcp: reconnected");
+        Ok(())
+    }
+
+    /// Request with automatic reconnect on broken pipe.
+    fn request(&mut self, method: &str, params: Option<Value>) -> Result<Value, String> {
+        match self.request_raw(method, params.clone()) {
+            Ok(v) => Ok(v),
+            Err(e) if e.contains("Broken pipe") || e.contains("os error 32")
+                   || e.contains("Connection reset") => {
+                // Connection lost — try to reconnect once
+                self.reconnect()?;
+                self.request_raw(method, params)
+            }
+            Err(e) => Err(e),
+        }
+    }
 }
 
 // ── Main loop ───────────────────────────────────────────────────