[Bug] Noticeable input lag and stuttering when connecting via Jump Host (ProxyJump) in v2.7

**Description**
I am experiencing a significant input delay and stuttering when typing commands in the terminal. This issue specifically occurs when connecting to a target server through a Jump Server (SSH Proxy/Bastion Host). Direct SSH connections to servers work perfectly with zero latency, but once a jump host is involved, the typing experience degrades noticeably.

**Environment**

* **OS:** Windows 11 / MacOS13+
* **WindTerm Version:** 2.7.0 (Bug present) / 2.6.1 (Worked perfectly)
* **Protocol:** SSH

**Steps to Reproduce**

1. Create a new SSH session.
2. Configure the session to route through a Jump Host (Proxy).
3. Connect to the target server successfully.
4. Type standard commands continuously in the terminal window.
5. Observe the noticeable delay between actual keystrokes and the characters rendering on the screen.

**Expected Behavior**
The keystrokes should be responsive and render smoothly in real-time without stuttering, identical to the performance of a direct SSH connection.

**Actual Behavior**
Typing feels heavy, with a distinct lag. Characters sometimes appear in bursts rather than smoothly following the keystrokes.

**Additional Context**

* This issue seems to be newly introduced in v2.7.0. I have tested the exact same environment using v2.6.1, and the jump host connection works completely fine without any input lag.
* I have tested the exact same network conditions and jump host configuration using other terminal emulators (such as MobaXterm and Electerm), and both handle the typing input perfectly smoothly without any stutter.
* I suspect this might be related to how WindTerm's custom SSH stack handles network buffers over proxy tunnels, or perhaps background I/O features (like Auto-Completion or SFTP directory tracking) are constantly blocking the main proxy channel.

Any advice or potential fixes for this proxy scenario would be greatly appreciated. Thank you for this amazing tool!

Reproduce the issue with a WindTerm SSH session routed through a Jump Host, then compare typing responsiveness between v2.7.0 and v2.6.1 under the same conditions. Check whether direct SSH remains unaffected and whether the lag is limited to ProxyJump connections. Done means commands render smoothly without bursts or noticeable input delay through the proxy.

Written by the indexing model from the issue text.