fix(ssh): fix windows openssh agent detection logic (#10954)

On Windows, checking for the existence of the OpenSSH agent named pipe
(`\\.\pipe\openssh-ssh-agent`) can throw an `EBUSY` error if the agent
is running and the pipe is in use. Previously, this error was caught
generically and treated as the pipe not existing, causing auto-detection
to fail even when the agent was active.

This change updates the detection logic to explicitly catch `EBUSY`
errors from `fs.stat` and treat them as a positive signal that the
pipe exists.

tabby-ssh/src/session/ssh.ts

@@ -248,7 +248,17 @@ export class SSHSession {
     private async getAgentConnectionSpec (): Promise<russh.AgentConnectionSpec|null> {
         if (this.hostApp.platform === Platform.Windows) {
             if (this.config.store.ssh.agentType === 'auto') {
-                if (await fs.exists(WINDOWS_OPENSSH_AGENT_PIPE)) {
+                let pipeExists = false
+                try {
+                    await fs.stat(WINDOWS_OPENSSH_AGENT_PIPE)
+                    pipeExists = true
+                } catch (e) {
+                    if (e.code === 'EBUSY') {
+                        pipeExists = true
+                    }
+                }
+
+                if (pipeExists) {
                     return {
                         kind: 'named-pipe',
                         path: WINDOWS_OPENSSH_AGENT_PIPE,