ssh-client keeps ~/.ssh to what it knows: sweep every other path into a kept folder (issue 1017, ADR 0415)

ssh-client owns ~/.ssh, but treated every file it did not place as found, so a
predecessor's drop-in and old copies stayed there for weeks. Its process now
sweeps at start and every ten minutes: keys at any depth (and links to them),
authorized_keys, authorized_keys2 and sockets stay, and a folder holding one is
gone into; everything else moves to ~/.local/state/ssh-client/retired/<UTC
time>/, a folder never shared with another sweep, with a list beside it, which
ssh_client_check shows. Nothing is deleted.

modules/ssh-client/cmd/ssh-client-tools/client.go

@@ -809,13 +809,17 @@ func (c *Client) Check(ctx context.Context, scan bool) (map[string]any, error) {
 	if len(debris) > 0 {
 		add("note", dir, "backups and retired copies lie beside the live files: %s", strings.Join(debris, ", "))
 	}
+	retired, err := c.Retired()
+	if err != nil {
+		add("problem", filepath.Join(c.Home, RetiredDir), "cannot be read: %v", err)
+	}
 	problems := 0
 	for _, x := range f {
 		if x.Severity == "problem" {
 			problems++
 		}
 	}
-	return map[string]any{"ok": problems == 0, "problems": problems, "findings": f, "keys": keyList, "debris": debris, "not_checked": notChecked}, nil
+	return map[string]any{"ok": problems == 0, "problems": problems, "findings": f, "keys": keyList, "debris": debris, "retired": retired, "not_checked": notChecked}, nil
 }
 
 // meshIncludeFirst is whether ~/.ssh/config begins with the mesh's region and it includes config.d.