do not enable OSC 7 support for old 5.x powershell (#2485)

fix for #2471, and better debugging for #2481

Author: sawka

pkg/remote/conncontroller/conncontroller.go

@@ -487,6 +487,7 @@ func (conn *SSHConn) InstallWsh(ctx context.Context, osArchStr string) error {
 	}
 	if err != nil {
 		conn.Infof(ctx, "ERROR detecting client platform: %v\n", err)
+		return fmt.Errorf("error detecting client platform: %w", err)
 	}
 	conn.Infof(ctx, "detected remote platform os:%s arch:%s\n", clientOs, clientArch)
 	err = remote.CpWshToRemote(ctx, client, clientOs, clientArch)

pkg/util/shellutil/shellintegration/pwsh_wavepwsh.sh

@@ -12,6 +12,10 @@ Remove-Item Env:WAVETERM_SWAPTOKEN
 # Load Wave completions
 wsh completion powershell | Out-String | Invoke-Expression
 
+if ($PSVersionTable.PSVersion.Major -lt 7) {
+    return  # skip OSC setup entirely
+}
+
 $Global:_WAVETERM_SI_FIRSTPROMPT = $true
 
 # shell integration