SSH connection status indicators

- Add Connected bool field to vfs.Entry and RemoteMount
- Track connection status in sshState.connectedHosts
- Show status icon (connected/disconnected) in pane header when browsing remote host
- Async SSH connection test with cancel support for Add Host dialog
- Colored labels and styled help text in SSH dialogs
- Confirmation dialog when deleting manually-added SSH hosts

vendor/golang.org/x/sys/cpu/cpu_loong64.s

@@ -0,0 +1,13 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+// func get_cpucfg(reg uint32) uint32
+TEXT ·get_cpucfg(SB), NOSPLIT|NOFRAME, $0
+	MOVW	reg+0(FP), R5
+	// CPUCFG R5, R4 = 0x00006ca4
+	WORD	$0x00006ca4
+	MOVW	R4, ret+8(FP)
+	RET