docs(telnet): correct envswitch/getpdo claims from #515/#471 measurements

Community hardware testing (bitranox, JRpersonal) on 2026-08-09 retracted
the earlier "inter-command delay is necessary" theory and established that
envswitch boseurls set commits the whole runtime layer (not just its two
arguments), has no read form, and doesn't ack with "OK". Corrects
TELNET-MIGRATION-METHOD.md and TELNET-COMMAND-REFERENCE.md accordingly,
retracts the stale "confirmed necessary" command-delay claim in
enable_ssh.go/cmd_setup.go, and lowers DefaultTelnetCommandDelay 5s -> 3s
as a smaller hedge now that the delay itself is known not to be the
mechanism.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

cmd/soundtouch-cli/cmd_setup.go

@@ -661,9 +661,8 @@ func setupEnableSSHCmd() *cli.Command {
 			&cli.DurationFlag{
 				Name:  "command-delay",
 				Value: setup.DefaultTelnetCommandDelay,
-				Usage: "Only affects --full-config: pause between each of its 6 steps (5 commands + reboot). Confirmed necessary on a real device (#515) — " +
-					"the same commands sent back-to-back left sshd down after reboot, but succeeded sent one at a time with ~7s gaps. Raise this if the " +
-					"default doesn't work on your device; 0 sends everything back-to-back (the old behavior)",
+				Usage: "Only affects --full-config: pause between each of its 6 steps (5 commands + reboot). " +
+					"Raise this if the default doesn't work on your device; 0 sends everything back-to-back",
 			},
 			&cli.BoolFlag{
 				Name: "no-auto-pair",