fix(mcp): use Content-Length framing for all responses

Adds writeFramed helper to send responses with HTTP-style Content-Length headers instead of raw JSON lines. Ensures compatibility with Claude Code which expects framed messages. Updates both main loop and writeResponse to use consistent framing.

main.go

@@ -110,8 +110,8 @@ func main() {
 
 		debugLog("Response: %s", string(response))
 
-		// Write response to stdout
-		fmt.Println(string(response))
+		// Write response to stdout with Content-Length framing
+		writeFramed(response)
 	}
 }
 
@@ -211,7 +211,11 @@ func readMessage(reader *bufio.Reader) ([]byte, error) {
 
 func writeResponse(resp interface{}) {
 	data, _ := json.Marshal(resp)
-	fmt.Println(string(data))
+	writeFramed(data)
+}
+
+func writeFramed(data []byte) {
+	fmt.Fprintf(os.Stdout, "Content-Length: %d\r\n\r\n%s", len(data), data)
 }
 
 func debugLog(format string, args ...interface{}) {